No you’re not taking crazy pills, it’s just you thought you saw an Elite caliber player, who wasn’t actually as Elite as he looked.
He played in scheme that best benefited his skills & elevated his productivity, but it wasn’t just because he was an all-world DT, it was because the scheme made him look like that.
Once he had to win matchups on his own without the benefit of being protected by an advantageous scheme, NFL scouts saw he simply wasn’t good enough to make a roster.
It happens more often than you might realize, a lot of players look like HOF’ers in college & then get to the league & just can’t hack it.