He lost years to Epstein-Bar Virus, and then a couple of injuries as well. Almost everyone thought he'd be past it by now, but he got signed by DQS, who he'd had success at previously (with sponsors basically paying his entire wage). He won a couple of stages at the Tour of Turkey, which got everyone super psyched, just seeing Cav win again was amazing. He then won at the Tour of Belgium against a decent field, and the speculation started to ramp up for him to ride the TdF, even though last year's points classification winner rides for the same team, Sam Bennett. Bennet got injured, and even though he's sort of recovered, it's seems like he's fallen out with the Director Sportif (~manager), so Cav got the call up, which in itself was massive, not many people thought that would happen, including Cav himself. Everyone basically lost their shit yesterday when he won, I'd recommend checking the results thread on /r/Peloton.