VCs can be wildly successful making 999 losing bets, as long as one bet is a 100 bagger. VCs are running off imperfect information, they don't know which horse will be a winner, so they spread their bets. The more bets the better.
Short hedge funds are betting that they know more than Mr Market, one of the most efficient pricing mechanism known to man. A long fund can be no smarter than a monkey throwing darts, and it still does well. A short fund needs to be the smartest person in the room. They go deep, to find an edge that no one else but them has spotted. So they are highly concentrated, because you just can't go that deep on more than a handful of companies.
To say a short sellers insight is not worth anything because they just got lucky once is incredibly... short sighted?