Probably because Chuck needed to beat Randy to become the champ, at which point he was dominant.
I don't think he beat Chuck in his prime. It was almost like, Liddell got good AFTER Randy beat him. IDK, just seemed that way. Tim Sylvia is not a big win, Randleman I'll give you because it was at the time, his wins aren't really all that impressive NOW. But, if you look back at the time he was winning, they were very impressive. That's why he is so popular with fans, not because of NOW, but because of THEN.
I agree, though. If you look at Chuck's record, he was at his best after beating Randy at UFC 52. He won the belt, defended it four times and stopped his opponent in every successful title defense.
However, the highest point in Chuck's career (in terms of performance) was before his first fight with Randy. After the loss to Jeremy Horn, he won eight straight in the UFC, beating Jeff Monson, Kevin Randleman, Murilo Bustamante (who would win the UFC middleweight title in his very next bout), Amar Suloev, Vitor Belfort (already debunked by Randy, but certainly very good) and Babalu.
That really was the part of his career that has his biggest wins. Of course, gotta have the belt to really be a legend.