How do you know Kotick was the one who who made Blizzard perform so horribly? Wouldn't that be on the CEO that just stepped down Mike Morhaime? Like, y'all want to call out Bobby, sure, but no one is actually showing he meddled so much into Blizzard that he caused WoW to decline in subscribers, made them miss opportunities like Dota 2, cancelled Titan and released Overwatch, made Diablo 3 and Starcraft 2 the shit game that it is. Bobby didn't do this to Blizzard, Mike did.
Where was Bobby's mistake, though? The gaming environment changed drastically. Like, people were going for MOBA early on, and now they go for Battle Royale. Things were different 10 years ago: streaming, mobile, and that online games are very popular. These trends change quickly so adapting to the market is harder than you would think.