Sure the TV deal is nice & the marquee names on the schedule has increased, but let's look at this objectively. In 4 Years of independence...

2011: 10-3, #25 (Coaches)
2012: 8-5, unranked
2013: 8-5, unranked
2014: 4-3 (I'd project 8-5 again based on the current trajectory of the team)

...now compare it to the last 4 seasons in the MWC

2007: 11-2, #14
2008: 10-3, #25, 21 (AP, Coaches)
2009: 11-2, #12
2010: 7-6

Maybe it's unfair to measure against one of the strongest stretches in recent history...but it's debateable.

So what is the difference? Well, primarially, in those years Bronco was rarely upset by lesser teams...even though the schedule was tougher overall. I think the reason for that is that the team had a goal, win the conference championship, and it was typically in play right up until the very last week of the season. Without that goal, the coaching staff can't motivate the team from week to week. After one loss (maybe two, with a schedule like '13, '15) the bowl is locked in, the season is over.

Even though the MWC wasn't great, it was something...now there is nothing motivating the team.