IMO, the Tebow trade is one of the worst decisions I've ever seen the Broncos make.
Tebow won eight games for them last season, including a playoff game against the Steelers. He generated revenue through jersey sales, kept attendance at the games up, and was clearly difficult for a team to completely prepare for (or play a 60-minute game against). He showed the potential to be at least a good quarterback with some throws, like the DeMaryius Thomas td in overtime against the Steelers. All he needs is a decent quarterback to show him how to actually throw the ball, which is what Peyton Manning would have done.
Also, Peyton Manning is only a temporary answer. I don't believe he will play out the 5 years on his contract. The Broncos need a quarterback after Manning, and at this point, they don't have one. Tebow would have made sense for this role. I think Elway hated Tebow becuase Tebow isn't the same type of quarterback as Elway was and Elway couldn't stand how the fans reacted so positively to Tebow. Elway even agreed to the Jets paying the Broncos less than Tebow's contract stated to get rid of him.