Major fan support for the Phillies - as opposed to the core support they've always had, even in decades of continual losing - is a function of winning, of being competitive. It's not a function of what fans think about the manager.
If you've been a serious follower of the Phils for 50 years or more, you will understand what I'm talking about here. The core will continue to be there. The rest? They turn out when the Phillies are winning, or when it's "fashionable" to be there (and the two are related). Moreover, for these fair weather fans, it's not really about the Phillies, and it's certainly not about "trust" of the Phillies. It's about making themselves part of something they see trending. It's "following the crowd."