Yup! It looks quite violent, doesn't it! I try my best to do a clean cut, but it doesn't always work out. There are loads of reasons to chop. Some just do it for propagation. I only do it if there's a need.
In this case, the base of this cactus was completely shriveled up, making it unable to absorb water. I've dealt with serious root rot cases, this seems to be the opposite; too little water, too much sun. Basically, reasons adjacent to the ones that caused the demise of my lithops. You can see one of the chopped parts there looks quite shriveled. That's where it started.
As for what I'll do with these pieces, I'll let them callous over for two days, then place them on soil to grow roots, and hopefully grow