They both had a fluke, but it's not something bad. If you are the best team in the world for 1 week, it's a fluke, but you still were the best team in the world, that's what count.
C9 deserved it, won against the 3 favorites.
For Gambit, the problem is not that they had a fluke, it's that most of their campaign through the major looked like a t2 tournament. Beside Astralis, they got only pretty average team, and the level of play was really low compared to other tournament. They could still pass Astralis and had to elevate their level for this one, but having only one real obstacle to get a major win is maybe not enough.
Not their fault tho, but I don't think they would have won if the favorites didn't eliminate each other and if the level was as high as usual.