First of all, a lot of that uranium seems to have been there and slowly decaying for a long time. I think, what we humans did was to “wake it up” and turn it into some more violently-reacting other elements, for the sake that we get the energy out of it at an acceptable pace. Now, though, it’s severely more dangerous than it was before.

it's weird, but it's not "more violent" it's just more energetic. Either through enrichment, making it more potent, which is an industry standard across the entire western world. Or through making fertile material, like uranium 238, fissile by going through the decay chain until it becomes something more spicy, like pu 239 or whatever.

The big problem is that the energy it releases is definitionally incompatible to human life. That's the ONLY problem.

oh and btw, nuclear reactors are physically incapable of "going critical" it's physically impossible. 90% of the concern is it breaking containment from being really fucking hot, which is notably, really hard to deal with.