Cloudflare’s business also depends on not messing with your traffic, right? It would certainly be easier for them to get your users’ content than for Amazon to do the same, but I think you still have to accept that risk with either. “Hypothetically being able to but not doing it” isn’t a whole lot of confidence if I were hosting some kind of shady website.
Sure, but since Cloudflare’s business is actively "messing" with all your traffic, all the time it's a smaller technical step to do it some more, and can also lead to accidents like cloudbleed. Every step that has access to unencrypted data is a potential attack vector or might be logging/leaking data.
