I think it was a combination of a lot of things: Daigle's drive, or lack their of, his attitude/general conduct (remember that hijack comment in an airport in 1996), and the apathy that set in after that cushy $2.5 million per contract in 1993.
But Daigle was a one-tool player in junior. He always had blazing speed, and he could use that against the opposition in junior. But at the NHL, he faced better skaters. He was still quicker than most of his opponents, but he didn't have the other skills. His hockey sense, puck handling and shot were below average, and he wasn't blessed with good size or determination, either.
As for Jim Carey, the guy benefitted from having one of the strongest defences in the league. He was exposed when injuries beset Washington's defence in 1996-97, and was really shown to be a fraud when he went to Boston. Most goalies in the league could have put up the numbers he did playing behind that defence in 1995-96.