Thanks a lot for this. I'll have a lot to think this weekend.
99% of all people are indeed not actively malicious by default but they can be so wrongly incentivized that the end result mimics malice very closely anyway.
Understand the problematic people's motivation if you can. It will help you devise a strategy. If not then maybe it's time for some good old top-bottom management with "you are here to obey orders, bucko".
So looking at incentives first is good place to start. Those experienced devs can be great asset if they can feel they can change behavior now.