That’s not the reason I’ve heard. You’re right that it was originally handed over because of the city’s bankruptcy (which did actually happen, not just nearly),

That’s not the reason I’ve heard. You’re right that it was originally handed over because of the city’s bankruptcy (which did actually happen, not just nearly), but the underlying reason wasn’t tax revenues: it was because the state wanted a bargaining chip for future negotiations, and unifying NYCT with the rest of the nascent MTA was an ideal one. (To my knowledge, the MTA is not significantly availed of the general state budget. They get some money from it, but not disproportionate to the amount their service base puts in via transit taxes.)