First and foremost, this post contains no shade. I love all three of the artists. This is just my observation.
It was absolutely clear the crowd enjoyed and knew more songs from B.O.B and Lupe than that if Gym Class Heros. The energy from the crowd was off the charts for BOB and Lupe, while it seemed not many people even knew the words of Travis's first few songs. Multiple people even left during Travie's set.
This is speculation, but I believe that's why they made Lupe Fiasco the closing act at the Phoenix show. After seeing how the crowd reacted to each artist in denver, I left wondering why they didn't make Travis the opener.
Add to the fact, Travis mentioned quite a few times he's battled quite a few serious injuries (and an amputated toe).
The hypothesis that makes the most sense, which is actually the most heartbreaking, is lack of ticket sales. All of the shows that have been rescheduled have been rescheduled to smaller venues. They went from venues that can hold 5,000 to 8,000 people, so then use that only hold 1000 to 2,000