TLDR: Because neoliberals are leading us into oblivion. The current state of politics in Europe is completely dysfunctional. Just as Trump is a symptom of economic and political collapse, so this this.
Like are you for or against Europe joining sanctions against Iran? Are you for or against Europe enacting sanctions against Israel and the USA? Find one of the established parties that is on the right side of these things.
Say what you want but I think "Le Pen has pledged to take France out of NATO and the US sphere of influence" is wildly popular. You say Le Pen is insane and people voting for it is insane, but the alternative parties and media you consume are insane as well. People are increasingly in a dream world and blaming Russia or China for all our own failings (including far right parties).
Just to be clear I do not support Le Pen's racist and Islamophobic rhetoric one bit and do not intent so vote for any far right party. But there isn't a single sane electable mass party right now in Europe that hasn't continued to support the US and Israel in their genocide and imperialism. I think only Spain's Pedro Sánchez Pérez-Castejón and suddenly found himself in lots of "scandals", but I have to read up on that.
Europe is chaining itself to the collapsing US empire. None of them spoke out against the attacks on Iran or Venezuela. They are cowards not leaders and will bring Europe to ruin. I strongly dislike the far right politics - but the cause of that is neoliberal politics so I hate them more.
It's INEVITABLE these parties will come to power. INEVITABLE! Why? Because people simple do not like more and more immigrants, refugees or otherwise foreigners in their countries. They simply don't. There could be like a billion refugees until 2050. This is some basic animal instinct shit that you can't argue away. And by painting ANY sensible policy against immigration as fascist they actually strengthened the actual fascists like Le Pen or AFD in Germany or Örebro in Sweden.
And because our economic future is bleak and the neoliberals have captured all mainstream parties and believe in NOTHING. They know nothing but do more neoliberalism.
And not everyone is so crazy about confronting Russia and escalating to WWIII. Why would any halfway selfish person in Europe want to ruin their own country over Ukraine? Fuck NATO.
So what's left? Either hard right or hard left.
And the democratic socialist parties almost face MORE resistance and smears against them in the media.