This is the way. As the studios decided they could make more money by becoming a streamer than they'd ever make with licensing deals with Netflix, they quit making those deals. As the deals would expire, Netflix would start removing them.

I always thought Netflix probably could have made licensing deals on their CDN. Lots of early streamers had issues (still have) with their CDN. Then again, the studios would probably want a clean break because they are so good about every thing they do (yes, that's sarcasm).