I’ve been playing cricket at senior level for 33 years - there’s a big difference between rubbing a bit of sun cream on the ball as opposed to taking a piece of sandpaper out with you. One is pushing the boundaries and one is straight out cheating.
zipper on the ball is just as bad. bottlecaps from the Pakistan team was a classic. Its been a part of cricket for yonks and nothing i've seen is telling me their transgressions were approximately 10x worse than anyone else had previously been sanctioned for. Their ban was the kind of ban you get for match fixing.