Trinidad's problem was that he was somewhat limited in his skill set. He was partially exposed by De La Hoya, although it was masked by the fact that Oscar took his foot off the pedal for the last four rounds of the fight and blew an easy decision. Bernard Hopkins didn't make the same mistake, and in one of the most incredible, clinical boxing displays ever, dismantled Trinidad to score a 12 round TKO. Felix had no idea what to do, and the look of confusion and bewilderment on his face in the later rounds really said it all.
Great exhibition of skill by Hopkins, just absolutely brilliant. If you haven't seen it, you need to go to YouTube and check it out.
The other weakness with Hopkins is that he could never recover from a defeat. After the Hopkins fight, he had one fight against a tomato can and then retired for a few years. He came back with a resounding win over a tailor-made opponent in Ricardo Mayorga, but then got thoroughly outpointed by Winky Wright and once again went back into retirement. Psychologically, he just didn't deal with defeat well.
I've always had a little more respect for guys that can recover from defeats. Joe Louis was KO'd on his way up by Max Schmeling, but Louis learned some lessons and went on to become one of the greatest champions ever (and utterly destroyed Schmeling in the rematch). Ali lost to Frazier and Norton, and was able to beat them in rematches and then regain the title by KO'ing Foreman. And don't forget Floyd Patterson - annihilated by Ingemar Johannsen and came back a year later to render Ingo unconscious while becoming the first heavyweight to regain the title. Gotta respect guys like that.
Trinidad in that aspect reminds me of another guy I wonder if any of you remember - Donald Curry. The guy was on the rise, had the unified welterweight title, and then ran into a buzzsaw named Lloyd Honeyghan. Never the same after that.