Other than Texas, I think there are OK reasons why the other programs aren't good/aren't good anymore.
Miami is one of the most interesting and unique programs in all of CFB. If you look at them just in terms of national championships won, they actually have been a wildly successful program (5 national titles since 1983). However, despite their football success and overall image they actually are a small private school with a good academic reputation, and the academic side and athletic side are in perpetual conflict. Miami isn't quite the academic school that Vanderbilt is, but you can kind of picture them like if Vandy had these periods of time where they were really good at football, even winning multiple titles. Weird, right?
As for Colorado and Nebraska, I think those schools are places that you actually shouldn't expect to find great programs. A huge part of Nebraska's story I think is just for that reason...you wouldn't necessarily expect a CFB powerhouse to come from there. Neither Nebraska or Colorado are high population states, neither produce much football talent, and both states are relatively far away from locations that do produce football talent. At present, both are poor fits in their conference. The only things Nebraska has going for it at the moment are their history and a large, passionate fanbase/administration that will spend money and try to improve the program. Colorado, unless I'm missing something, doesn't really have a whole lot going for it.