I can actually relate to that, especially in a big co where you hire fast. I think it's shitty to over-hire and lay off, but I've definitely worked in many teams where there were just too many people (many very smart) with their own sense of priorities and goals, and it makes it hard to anything done. This is especially true when you over-divide areas of responsiblity.
Stepping down vs mass layoffs reduces headcount by 1/20th, so the only other solution is to continue floundering until everybody loses their job. These people complaining about layoffs would prefer the whole plant to rot versus pruning a few wilting stems.
Agreed on the pay cut - even if temporary - and aligning incentives. Resignation frees them from a chance to correct their missteps. Just making a guess here, but I would think that, in general, good people who actually hold themselves accountable for screwing up understand the situation better than a replacement. Unless there is a pattern, it is probably in the org’s best interest to give that manager a shot at redemption, especially considering the glut of incompetent managers, the learning curve for competent managers, and the likelihood that a replacement would do a better job.
If an engineer screws up hugely, do you want get rid of them immediately and find a replacement, or evaluate whether or not they learned a very important and expensive lesson that may happen again with a replacement?