Bicycling

I'm just a fan, man, you'll have to explain what you mean. I know it's a team sport but are you saying the other teams gave up?

the rest of jumbo kinda let him go for it

Kind of, but that stuff didn't happen in a vacuum. Sepp was able to get into the breakaway in the early stages mostly because the favorites were looking at Roglic and Vingegaard, thinking they were jumbo's plan and at most he'd be set up as a satellite rider to support them in a later attack. It was probably not expected that he'd end up with 2 minutes on GC, and when he did, that put the team under a lot of pressure to not be seen as attacking their own guy.

In the end jumbo did a pretty good job of supporting him (as opposed to tasking him with riding for Roglic or Vingegaard) but he still had to do the winning himself. He's super-strong and I thought it was hilarious to hear the commentators expressing surprise that he could time trial as well as he can- I guess they'd decided he was just a climber. (but really, in his role as superdomestique it doesn't make sense to go hard in time trial days, and as GC leader it absolutely made sense for him to do that)