If I had to guess, it's capacity that's killing everyone. When all these guys were nascent funds with a few hundred under management, it was easy to find opportunities that were off the beaten path. Long-short guys were able to invest into companies as small as 150-200mm in market cap. Nowdays every one of these dudes is sitting on a few billion AUM and that forces them to invest into the same crowded ideas.
A one way street seems easy to navigate, but for long/short strategies and active traders it's not that easey... It's like we're sailing in unchartered waters and if you keep going in the same direction you know where you're heading... but when you veer off and try someting else... that might backfire...