Nobody on Earth reads the entire manual before starting up some software; it's the vendor's responsibility to not have insensible defaults like "delete my local versions of files without asking me"
True. We have reached this level because of our complacency, and not due to Apple inherently trying to be malicious towards people like OP. The vendors are responsible to have sensible defaults, but we can't buy their products, use their software, sign up for their services, and then complain about malice when the vendors are delivering exactly what we signed up for and agreed upon. I'm just trying to say that OP should focus his energy on being more self conscious about what he signs up for rather than claiming that Apple is stealing his data. He gave up ownership of the data the moment he agreed to the TOS. What Apple is doing is counterproductive and just illogical from a UX point of view (in my opinion) but they did not steal OP's data. The title is a bit clickbait-y in that sense.
Well, they took a copy of it, compressed and maybe in a different version (which is more or less what they advertise) but then also irretrievably deleted the original, which is what he's upset about. Maybe "steal" is the wrong word; it still seems outrageous.