30 years ago - in the mid-1990s - 100% of all terror attacks were carried out by white Christians, often by groups like the Irish Republicans.

Can you give an example of even one "islamist" attack from that time period?

what evidence is there that this registered republican was "far left"?

I have no recollection of any of those perps being left-wing. Apolitical and centrists.

Islamism is a far-right ideology. Islamists even collaborate with other flavors of far-right. A lot of American leftists don't like talking about it because they also want solidarity with liberal and leftist Muslims, and the biggest vulnerability to that solidarity is for the American right to demonize Muslims by pointing out that there's an Islamist right. The far right is always inherently scary to anyone outside the preferred in-group.

> Leftists somehow tried to dissociate themselves from all the socialist promises that got Hitler elected.

Even though the Soviets and the Nazis did collaborate, Hitler wasn't a leftist by any definition of the word. Both sides of the collaboration hated each other's guts and figured they'd be able to beat the other once they silenced their mutual threat: liberals and liberal socialists[1]. Hitler was clearly sponsored by German and American[0] business interests looking to maintain their wealth by any means necessary - including putting a meth-addled idiot in power. Everything that "seems socialist" about Hitler (or Stalin[1], or Trump, or Napoleon) is either a concession, or a lie, made to fool people at the margins of the left wing.

The ultimate goal of any fascist is to divide and conquer the people by using non-class divisions (e.g. race, language, religion) to keep the people from realizing whose boot is on their neck. In America this was "Why would you join a union? Do you want to be paid the same as a black person!?". In Germany this was "Why would you vote socialist? Don't you know the Jews made that up!?". The labels are different but the effect is the same: don't join together and fight us, your friends and neighbors are your real enemy.

> And it's kinda, sorta, indeed not a world where "far-right" terrorism ain't that much of a big thing.

It stops being far-right terrorism when the far-right is in power. There's no need to maintain a large insurgency against... what, exactly? Yourself?

[0] Casual reminder that Henry Ford was a huge Hitlerite and that cars are inherently Hitlertech.

[1] Hitler was an example of what happens when the reactionary counter-revolution succeeds. But there's a second possibility: the reactionaries only succeed at pushing the left in a far more authoritarian direction. A Reign of Terror happens, in which both the reactionaries and left-libertarians are purged as equal traitors to the revolution. This continues to burn through the political hierarchy until the forest fire runs out of fuel to burn, Robespierre is hung by his own guillotine, and Thermidor comes. Russia's communists went down the same path the French left did a hundred years ago, and that's why you sometimes hear socialists say "true socialism has never been tried".