I left ISD in Sept 2017 after 10 years. It was toxic for at least my last 3-4 years there. They were gutting entire departments. Ageism was rampant getting rid of the older associates. The writing was on the wall and I left. I did get a better paying job and like the OP, my next job was less stressful, more relaxed and I was having fun at a job again.
I left before the rank and yank took effect. Once you have that target on your back, you may as well polish up your resume and start looking. I heard one associate had medical issues and got targeted and was termed with 60 days to find a new job within the HO. They turned around and filed for STD and got it. Then filed for LTD. They got it. WM has to pay 75% of their salary and their benefits for life!
I am hearing that the HO can't get high quality hires anymore because of their reputation. And that the good people they having are fleeing in droves. I'd like further confirmation on these two. Those that do hire in ISD, get some experience under their belt and leave for greener pastures. Those that stay are hoping against hope they can actually retire.