The Dodgers did NOT do poorly before leaving Brooklyn. They were drawing over a million a year. (In those days, that was a big number.) By contrast, the Giants drew a bit over 200,000 their last year at the Polo Grounds.
The real issue was that O’Malley wanted to build a ballpark near Atlantic and Flatbush in the heart of Brooklyn, but the city’s chief planner, Robert Moses, wouldn’t allow it. (He offered land in the Flushing Meadow in Queens (about where Citi Field is now.)
Ironically, the site in Brooklyn that O’Malley wanted is now the site of the Barclays Center, the soon-to-be home of the Nets.
That's not exactly an inspiring figure, since they were in about the middle of the pack among major leage teams, despite the fact that they fielded superb teams with multiple future Hall of Famers and near-HOFers, winning NL pennants or coming close just about every year over the previous decade.
Clearly, there were lots of legitimate problems with small and aging Ebetts Field, not the least of which was lack of parking and deterioration of the surrounding neighborhood.
Comparing the building of a baseball stadium to that of an indoor basketball (and/or hockey) arena in a particular location is like comparing oranges to pineapples. The baseball stadium would have to accommodate more than twice the capacity of the indoor arena, causing more traffic congestion. It also would require a much larger area, including more parking facilities. Plus, the baseball stadium would host more games per year. Overall, getting a baseball stadium built is by far the more complicated task.
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.
[Walter] O’Malley wanted to build a ballpark near Atlantic and Flatbush in the heart of Brooklyn, but the city’s chief planner, Robert Moses, wouldn’t allow it. (He offered land in the Flushing Meadow in Queens (about where Citi Field is now.)The Dodgers may not have been doing poorly before leaving Brooklyn, but Ebbets Field was rendered obsolete before her time---nobody anticipated Brooklyn's postwar growth hemming the park in, and a pre-Rickey/pre-O'Malley regime had let the park go to seed enough that even Larry MacPhail's improvements to the park in the early 1940s were only going to hold it so far.
What Moses had in mind was what ultimately became Shea Stadium---he wanted to build a new multipurpose facility in Queens and jam it down O'Malley's throat. Moses had actually vowed that never again would a privately-built, privately-owned sports facility rise in New York so long as he ran the planning and building show in the city and the state. And New York's mouselike politicians weren't exactly going to stand up to the man, either.
What should be an intriguing historical question---if O'Malley was that adamant about not moving to Queens (If we play in Queens, we won't be the Brooklyn Dodgers anymore), why didn't Moses think about the Giants, who also needed a new ballpark in about the worst way possible (the Polo Grounds was a rambling wreck by the same time), who couldn't afford to build a new ballpark on their own, and who didn't have the strict borough identification the Dodgers had? Moses could have gotten what he wanted for his new ballpark (the Giants could have hung on awhile knowing they'd have a new home), and O'Malley might---might---then have been allowed, still, to build what he planned to build in Flatbush. So long as the Giants weren't even part of Moses' thinking, Moses had O'Malley over a barrel, even with O'Malley's political connections.