I think you're confusing national politics and local politics. DeBlasio has been Mayor for 4 years. The prior 20 years worth of mayors were Republican^. The Governors of New York have been 12 years rep, 12 years dem in that same time period.

^ Bloomberg flipped around parties for convenience of elections. In regards to this topic he would be on the conservative side given that he was constantly butting heads with the transit unions.