There are many professional athletes and performers who are not covered by the mayor’s “heter” not to be vaccinated. The key factor is whether you are producing large amount of revenue for the city and/or the mayor.
If team bias were a factor, the dispensation would have been only to teams based in Queens. If race were a factor, it would not have been extend to the NHL. An important factor is that the city employees being fired were guilty of independent thought, meaning they probably weren’t good Democrats (let’s be honest, thinking and being a Democrat is a bit of a contradiction), and of course, that the owner of the Mets is a big campaign contributor.