No he wasn't. If you're going to fire an executive because you don't think they're doing a good job, you don't do it out of the blue right after they finished making a bunch of big business deals. That's not how large corporations operate.
No clue if the cocaine stuff is true (there are rumors it was actually due to sexual harassment type allegations), but it definitely wasn't business related. ESPN was doing just fine with Skipper at the helm (it was probably Disney's most profitable division), which is why he had no trouble getting other executive positions shortly after.