Google employees do not usually have access to user data - only a very small subset of engineers do, and it's strictly controlled.

"Political activists" is just one (rather unlikely) insider threat among many that a company like Google has to mitigate.

That will be a problem with any company that doesn`t let you encrypt your data.

It is technically impossible for something like Protonmail to read my emails.

This feature does not exist with most other email providers e.g. Gmail.

Even if we drop the activist threat model there is still the possibility of external hacking.

Possibly organized crime. I heard of one Yandex employee caught selling access to Yandex users email accounts.

Maybe something similar could happen?

I do not know which internal systems Google or related companies have to prevent employees from accessing user data.

Does anyone here have resources on this topic?

What is not dangerous ?

Nothing. Therefore I'll go skydiving without a parachute; hopefully that water I can see down there is deep enough.

After all, not skydiving is also dangerous.

Wrong question.