Sign stealing is "ok" if it's done on the field as part of the on-field alertness. What the Astros did was far beyond that. They used technology in a systematic way. Way beyond normal Spy vs Spy gamesmanship. That's more like Mafia shit.
Ball tampering otoh...part of the game as long as you don't get caught. Some very high profile players are rumored to have done it, but they didn't get caught, so...
There's a latent criminality in every competitive endeavor, a with it comes lines that are generally agreed on that shouldn't be crossed - past a certain point!