Sorel is usually seen as a heterodox thinker because he has been influential in radical movements which are politically very desperate. This seems strange to a lot of people, but once you study his work it starts to seem perfectly natural. He has a whole thing about the importance of myth and the warrior ethos. Similar to what Plato advocated in the Republic in some regards. I think his most influential point though is the one which kinda pops the "oh so mysterious" bubble around him. He wrote a pretty solid and widely read defense of political violence called "Reflections on Violence". Naturally, any movement seeking to justify street violence will point to this, since it has name recognition and is only vaguely tied to any one political alignment.
I have attached a pdf of the aforementioned book. Unless you live somewhere with limited internet such that you can't access Russian servers though you definitely have access to Sorel's work (as well as most other books in general). Library Genesis is your friend.