Your argument makes no sense. Ganeshutsav is a festival that has been celebrated in all parts of Maharashtra from pre-independence days. It was in fact initiated by Lokmanya Tilak as a way to secretly convene freedom fighters to assemble under the guise of religious celebration to give voice to their fight against the British. Dahi Handi is a similar cultural phenomenon that has a long history of being celebrated among Maharashtrian communities. Politicizing or complete ignorance from politics for these festivals makes no difference to the average Maharashtrian community as these festivals are going to be celebrated any way. It is the festivals that are traditionally NOT celebrated in Mumbai that are under question here. Chat Puja, which is a new phenomenon is welcome if it's a purely religious festival, with the aim of increasing harmony and assimilation between existing groups of people. However, if it's sole purpose is flouting political muscle, which is the way it is largely being perceived for the last few years, then it's vaue is questionable. For instance, I challenge you to find a slogan like "U.P. Bihar to jhaanki hai, Mumbai abhi baaki hai" during the entire Ganpati festival. Or Dahi Handi.
Please don't mix cultural events with politics. Political support of cultural events and politicization of a cultural event are two completely different things.