ISIS is 95% of people of African and Middle-Eastern origins. Then maybe a bit of crazies from Indonesia, Chechnya, etc. As well, ISIS was founded in Iraq itself. How is it a "bunch of European"?
Here's a BBC article https://www.bbc.com/news/world-middle-east-47286935 and the report that it sources its data from https://icsr.info/wp-content/uploads/2018/07/Women-in-ISIS-r... if you care to learn more.
I think the parent comment was referring to the idea that the overwhelmingy majority of those "Europeans" we're rather people of MENA/Turkish immigrant background, not "ethnically" European.
TL;DR: ISIS was not "a bunch of European guys who got radicalized." It was mostly people from the Middle East and North Africa: somewhere between 75-93%. 95% MENA is probably not correct either, but it's much closer to correct than your original claim.