Many of the tech firms that are bleeding out have become everything they fought against. The MBA-isation of big tech is so jarring when you land in the valley coming in from Florida, Colorado or many a foreign country where the rules of engagement and speech are still "normal" ie, casual, ie, ideas win respect not rank, ie there are perspectives outside of what the headlines in techmeme alone speak to.
If you work at a large tech firm today, you will see this play out every 6 months in the promotion discussions that have essentially dissolved into political horse trading and are the single most important events to anyone not directly involved in very very senior roles (Where you speak to investors or are involved in company-level change)
This is so strange to live through as a mid/mid-senior level VP, Manager, Lead what have you. Here you are, apparently at the pinnacle of your achievement, having beaten thousands of intelligent people in competitive exams and studied at the most prestigious institutions only to . . . spend a significant portion of your promotion cycle trying to play the Game of Thrones with a bunch of MBAs ?
Compensation is not a significant differentiator anymore as it has been in the past, infact, one may argue, for the top 10-15% of the company that handles the most crucial products, quitting and starting up would easily get them overnight valuations orders of magnitude returns over their expected 20 year earnings were they to continue climbing the corp ladder (Nuvia, anyone?)
So, in short, the environment externally has changed. The environment internally has absorbed a lot of the lifers and MBAs from "Successful" incumbents to the point where the internal culture reflects everything that was wrong with those guys that these firms "Disrupted" and there's plenty of money to go around.