I don't line in Colorado but I can guess that a lot of conservatives were just a little bit troubled by having a candidate who's fortune was made from alcohol - there are a lot of Baptists, Mormons and other teetotalers who would have had to swallow some ideological purity to elect somebody who sold booze for a living.
Secondly, on a personal note, I'm really tired of watching candidates run for and win Senate seats for seemingly no other qualification than having a pile of money. After watching guys like Corzine, Dayton, Cantwell, etc. essentially BUY a Senate seat, I'd have prefered someone who was there because he was an ideologically conservative Republican rather than just a rich one.
I also have a problem with millionaires trying to buy power. Whatever happened to working your way up first? Maybe Coors should have resigned back in the 1990s and first ran for Colorado governor before thinking of buying a Senate seat. Sheesh.