So, let's say Mas and Lopez take 30s more time on the climb and Mas takes second spot in GC ahead of Roglic by a few seconds. Roglic doesn't care, right because he doesn't ride for 2nd or 3rd, he only rides to win. Then next week Evenepoel is out with Covid, and Mas takes red, and Roglic who didn't care about 2nd, takes 2nd. Yeah, that would have been stupid.It would've been incredibly noble of Roglic to help Evenepoel, but good grief that would've been stupid.
Every rider in front of you is an extra rider you have to pass if you want to win. So Mas was not just a threat to Evenepoel, he was not just a threat for Roglic' 2nd place. He was also a threat for Roglic in case he wants 1st place. He was inviting a 3rd dog into the fight.