Interestingly, the troubles the Dodgers had in getting a new ballpark built wasn't because Robert Moses "wouldn't allow it" . . . it was because Moses wouldn't use the City's eminent domain powers to condemn the land and give it to O'Malley for substantially less than it would have cost him to buy it outright.
A million fans a year would be very low attendance today, but was considered the standard in the 1950s and 1960s. So yes, it was good attendance. Especially considering the ballpark.
Moses was quite willing to use eminent domain to give the Dodgers land in Flushing Meadow, but he worked extra hard to keep O’Malley from being able to acquire the land at Atlantic and Flatbush. It didn’t fit Moses’s plan.