Indeed, positive audience sentiment has an expiration date. He rode the wave too long, perhaps, but it is hard to know when to stop. All ongoing media productions (e.g. TV shows) suffer from the same problem and question of when to keep going and when to move on.
So even if it was a longstanding thing, pushing the content toward a more millenial/gen-z audience is still a new direction and risk.
In the end, the biggest factor was the dissonance between his warm, cozy "all in this together" messaging combined with grocery price hikes and news like this coming on the other side of it all: https://www.blogto.com/city/2022/11/loblaw-report-profit-foo...
If people aren't eating at restaurants, it is almost certain they are getting their food at the grocery store instead. For all the mockery of Galen, it seems the marketing strategy has been unbelievably successful.
That's probably why he continued to cast himself even as the audience focus shifted to millennials and gen-z. Letting someone laughing at you for a few minutes is no big deal. Watching them love you when they show up at your store over and over makes it all worthwhile, I'm sure.