I'm not surprised by this at all. Viard's Chanel was a very commercialised version of Karl's Chanel, which made it easy to market to that audience. Younger women on the other hand don't want to dress like their mothers and Blazy's look fit the Philo-adjacent ideal that millenials like. Funny enough, in turn, Gen Z women seem to be rejecting that Philo-adjacent ideal in favour of something "prettier and girlier". Something like SS95 would be right up their alley.
In hindsight, I think that Viard needed to go, but I don't think that Blazy was the right choice for what the brand needs. The fashion operation only needed minor pruning and a refreshing pick-me-up, not a full aesthetical overhaul