Starting in ~2010 there was an absolute gold rush of investment in the tech sector - if you had a moderately good idea, knew how to put a proposal together and could get it in front of the right people, you could get $10-50 million without having to worry about little things like "how are we going to turn a profit" and "how will will we keep paying the expensive developers and infrastructure costs when the investment money runs out".

This has changed in the last few years - the money is drying up, and the investors that are left and much more worried about their investments actually having a business model and a path to profitability rather than just throwing money at people and hoping that Google buys them for 50x the original investment.

No special insider knowledge, but I'd bet this is what is happening - Plex probably isn't in a spot where they can sustain the current staffing and infrastructure costs purely out of existing revenue. They will be reliant on ongoing investment to let them keep developing rather than just keeping the lights on, and that investment will come with more conditions than it would have had 5 years ago - they will need to hit targets for number of accounts, percentage of paid accounts etc or they won't be getting further investment, which for a tech product is effectively a slow death sentence