The MBAs take over and implement KPIs that might even be well-intentioned but are ultimately easiest to satisfy by cutting corners. For example: KPI that measures market share of Edge; instead of making Edge better to increase its share, just screw your users by making Edge default on Windows on every other update.
I've seen it happen at my own company, and while I always had pipedreams that this isn't happening at the big tech players because there are too many smart folks around to stop that nonsense, I can well imagine that it boils down to these kind of bullshit reasons.
Quarterly Earnings reports. They've picked off all the low hanging fruit to show growth, now they're grasping.