I don't know you or your kids, but I can almost guarantee that this is not true at all, so please don't tell yourself that. You don't take credit for their good traits and accomplishments, right? :)
There are way too many variables involved, the largest being that they are each independent people. You have no idea how they would have turned out had you not been in their life - for all you know, things would have been much worse and your involvement was one of the things that made the difference. And their stories aren't finished yet... people figure things out at different times; they may yet turn out just fine and look back with gratitude to a stepdad who didn't write them off even though they gave him every reason to.
Don't let it bug you. People are how they are, more often than not. And your kiddos will probably relax in a decade or so when their testosterone levels start to drop.
What I'm saying is that I could easily be the guy in this story, because short of a blackout, I've got kids on VPNs who are looking at extreme content (because everyone they know does, apparently), thinking QAnon is real, etc., and whose capacity for disrupting everyone around them without a moment's thought of anyone but themselves knows no bounds. Pandora's box is open, and I have no idea how to close it. On dark evenings when we've had another gut-wrenching round of horror stories, I'd probably buy one if I knew where to get one.