It’s more like, millennials got older and started drinking less (as happens), and Gen Z drinks different things like hard seltzer, and also drinks a bit less overall. Plus there were just way too many craft brewers making hoppy ipa to begin with.

40% of the US population is older than 45, and millenial includes < 50th percentile.

We're also talking about alcohol consumption. Only half of Gen Z can drink and none of Alpha.