It is extremely easy for a government to infiltrate into these organizations and get their hands on it, it has happened at Twitter [1], for instance.
So, yes, the problem IS data collection in the first place.
1: https://www.washingtonpost.com/national-security/former-twit...
I do agree that data collection is at the core of the problem, but Twitter really should have done a better job.
No amount of "security" is enough for an actor who wants to do this and has privileged to the data. This is almost impossible to out-engineer, if you think a company like Twitter cannot solve "such an easy problem" you're being naive.
There's a shitload of data for sale from brokers. So foreign governments might not even need much from a company like FB. Perhaps just enough to confirm the validity of data purchase from other sources.