I think styles/expectations grew for comedy. We completely give up on a style once it runs it's course. They'll all come back in fashion again but it's trends.
Character actor films like Austin Powers, Love Guru or the Nutty Professor were seen as cliche.
Parody films like Scary Movie, Not Another Teen Movie, etc were getting stale.
Surrealist ran it's course with Napoleon Dynamite, Tim & Eric and other Adult Swim inspired shows.
Like him of hate him, Judd Apatow's style defined comedy in the early/mid 2000's and had his signature on everything he produced (knocked up, super bad, anchor man, etc). I think this is where we still are and we're waiting for the next trend to hit again.
Comedy doesn't really "hit" if we've been stuck in the same trend too long. Someone will re-popularize or start something new soon. My guess is it'll go to Jackass. Authentic reactions are always fun and that's probably why I watch more twitch/youtube atm.