It's completely to do with work from home. Everyone is fed up after what they had to deal with in 2020, and tech workers (almost 100% of them) got to work from home, many for the first time ever. After everything they've been through in 2020, it makes zero sense to willingly go back to work in an office where you put yourself at risk and have to deal with all those horrible things you had to deal with before 2020. So…
I work at a large company that changed to become remote first in 2020, and we are seeing similar rates of churn. I am not sure this is the whole story.
For most of us, we just tolerate the job/company we are currently at. Social events, camaraderie and a sense of "we are in the same boat" causes people to continue on. Then lock-downs came and suddenly all of that is gone. You are now stuck in isolation with the thing you actually deep down dislike or resent. Previously, going to the office was like fighting in a pit, but at the end of the day you got to escape by going home and decompress. But if you workplace is also your home, you don't get to escape anymore. The same computer/screen that used to bring you joy, now triggers ptsd/resentment feelings. Thus you are stuck with your demon, consistently, without reprieve/escape. Thus people let those feelings build up, often without knowing it, and when that bubble burst, they feel they need to run away and quit. Some might even start questioning their whole career path and the nature of the work, and thus the nature of our society and economy. Thus the whole drive to work gets short circuited by those feeling of resentment when you want to work again.
That's just my personal feelings around it. I get the feeling when I look at our Jira board. Those 10 minutes before standup starts, feels like an eternity. Our scrum master is no longer my "friend", I just see them as a person that cracks the whip at this point. All while being unable to escape it all, since I have stuff that needs to get paid. Oh, and all this is at good employer doing meaningful work. Cannot imagine other peoples' dread if they get stuck in the same loop.