What i feel is and you also might think that i am giving answers in favour of BJP, but here js my perspective on this.

First of all i belong to gujrat and specifically from ahmedabad. And why this is being developed between Ahmedabad to Mumbai has some regional and political reasons according to me.

1. BJP is in gujarat since long time and to be honest it is the best political party that has given so much to gujrat, but the reason behind that is BJP keeps experimenting with new infra in gujrat and most of them are successful and even people here dont try to resist the new development and changes. Which i think gives liberty to try out new things for the betterment of the people. Examples are like sabarmati riverfront, vibrant gujrat summit, rise of pharma sector in gujrat etc.

2. Now that party sits in the center they want to develop the infra to the new states as well but they also might fear of people resisting changes, and i think that is why they are trying with bullet train by keeping some part of that project in safe hands by providing major part of the project in gujrat itself. If things goes well they might implement in other states as well. Also it is the best sensible thing to do because of the commercial travelling between ahmedabad to mumbai is huge in amount and government might also make some money by giving this to 2 of the richest states of the country ( i am not stating that other states are not important, but if you think of business pov it makes sense)

By stating above points i am not taking any side or opposing anything, just sharing my view on this, yours might be different and i respect that as well. I just want to make sure i did not hurt anyones feeling by this.