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Last edited Mon Jun 4, 2018, 01:06 PM - Edit history (2)
It is very condensed and therefore, there are necessarily shortcuts and biases. Your seemingly simple question requires an answer that would fill entire libraries. 
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Yes and no.
Extreme trends have always existed, as far back in time as we can go.
The world has changed enormously particularly since the industrial revolution. Although globally beneficial for human evolution, these changes were indirectly influenced up to our time and almost certainly a direct cause of the Napoleonic wars. When Napoleon set out to conquer Europe, it was above all a question of controlling strategic entry points, in this case the ports, and of opposing the British, supporters of free trade and ultra liberalism. In other words, British did not want customs duties.
Does that ring a bell? 
The rest of Europe was more protectionist.
The European geopolitical map is being redrawn, the borders of some countries are changing, other countries have been born : Belgium as a sovereign state, has existed only since 1830. Economic progress gives rise to social demands and major political trends are in the making. The major ideological currents are gradually taking shape. The right to vote, and with it the right to speak, is also becoming more widespread. It is therefore necessary to seduce the elector and thus, to give substance to the ideas which one defends. Little by little, people who can read and write are increasing. The sciences are developing and adopting more rigorous methodologies than in the past, even if this is not to be compared with our current standards. Some questionable sciences, such as eugenics, will emerge.
Any politician who is even a little awake will draw support for his words from scientific work of all kinds. Napoleon is no longer there, but Europe is far from at peace. The tensions persist, in particular because of the colonial lusts of some nations: they look at the Ottoman Empire which weakens day by day, the papillae salivate, they sharpen their knives in preparation for the next dismemberment... to this is added the conflict between France and Prussia which will end with the war of 1870 and the famous loss of Alsace and Lorraine.
A small parenthesis to point out that contrary to popular belief, it was not the war of 1870 which was at the origin of the first world war. In reality, its roots go back to the end of the Napoleonic wars. In 1819, a series of small German states united. Napoleon III, who was a genuine idiot, set himself in mind to fight them to try to cement an unlikely union. ... On the other side, there was Bismarck, who was anything but a fool, the precursor of what we know today as Germany, saw the light of day... both France and Prussia, therefore, began to forge alliances (sometimes against nature) and here we are with the Triple Entente and The Triple Alliance which will literally trap one another and plunge the world into a world conflict later. The war was NEVER intended, but because of the alliances and allegiances, and the blindness of Wilhelm II who wanted to push Serbia onto the ropes . Austria-Hungary delivered to Serbia " the July Ultimatum", a series of ten demands that were made intentionally unacceptable, in an effort to provoke a war with Serbia.
In fact, no one cared about Francois-Ferdinand of Austria, but since he was kind enough to run for the scapegoat role and got himself murdered..., Wilhelm II shouldn't have missed the opportunity, should he? 
Let us close the parenthesis and return to political movements.
Russia is in the grip of serious internal, social and economic problems, the quasi-feudal regime that still governed it will favor the development of extreme leftist movements. Germany, after the first world war, was confronted with a calamitous economic situation, amplified by the treaty of Versailles. Already disastrous in itself, the treaty did not take into account the realities of the time, and reinforced humiliation in Germany. And here comes Hitler, a failed artist, a little character who is embittered and full of serious psychological problems. He thus launches into politics, refines his nauseating theories and encourages the emergence of the extreme right.
After the second world war, nations understood the disaster of a nationalist and xenophobic policy. From there on, everything with extremist connotations with a racist tendency has been isolated and banned. At least, for what concerns the far-right.
After that very, very long introduction, i finally come to answer to your question.
For a while, extremist xenophobic tendencies were contained, by laws and by economic growth and therefore, as soon as people have a full stomach, they are no more terribly excited at the idea of launching a revolution. Alexis de Tocqueville said it: you don't make revolution with people who have a full stomach.
Then comes the oil shock of the 1970s, the successive economic crises and the disarmed politicians, whose margin of maneuver is very limited because of the post-war world order, which has seen the emergence of international treaties, globalization, etc.
From there, xenophobic parties, which never actually disappeared, found a renewed interest among certain social categories, especially the rather frustrated and poorly educated. This association remains, if not anecdotal, at least limited. Moreover, no major traditional party would have compromised itself in such a tasteless alliance.
But the major parties started losing a little ground to the small extremist parties and so some otherwise traditional politicians will try to recover support from extremists by dressing one or two ideas with a pseudo patent of respectability, on the pretext that if the extreme parties prosper, it is because we ignore the demands of their base!
From then on, hate ideology became a little less unacceptable. At the beginning, it has worked : recovered traditional voters still prefer not to compromise too much.
But as this is a short-term view, solely political and rather populist, the only result achieved is even greater frustration among disappointed voters.
Besides that, extremist parties have understood the necessity of disguising their message and smoothing their words, while keeping their business intact : selling hatred, dividing, choosing a scapegoat and seducing with simplistic messages and proposing even more simplistic solutions, which have no chance of being applied and even less of succeeding.
In the end, they have gained more and more confidence, they claim protection for their dubious speech in the name of freedom of expression, and they have enticed all the frustrated voters.
I am so mad at politicians for opening Pandora's box! 
Because basically, the Le pen, Farrage, Wilders, Trump and company have only one objective: to do exactly what they claim to fight, that is to say to take advantage of the system, to live at the expense of others, and especially not to take responsibility nor to make the least effort of facing the consequences of their speech and actions.
In short, to have a paradisaical parasite life!