No they didn't. They waited because it was profitable. Balmung's uneven population totals were evident before Heavensward even launched. They had years to address it and did absolutely nothing. SE didn't give them anything as the server stayed locked despite what amounted to only a handful of complaints. And we're once again back to this congestion nonsense. You know what caused the DC to implode? The devs put an instance roughly ten quests into the MSQ, thereby making it inevitable virtually every single player would all attempt to queue at nearly the same time. If it were merely a Balmung issue, why did Primal and Chaos also explode? NEST even posted a mock video where Drak waited two days to access Duty Finder. Going a step further, this exact issue occurred again during Deltascape. Why? They put another instance almost immediately into the quest chain. Yoshida even admitted outright that caused the servers to crash.
The other issue is their auto log-off system is laughably easy to exploit. Target a market board, craft, summon your retainer; the list goes on. This rendered it useless since people were sharing how to get around being logged out even in-game. Now yes, Balmung obviously had a larger volume but every server had people doing this. The queue times subsided when they implemented a forced log out. Even Balmung had queues less than ten minutes afterwards.
Good for you? While you may not harbor attachments, others do. And once settled into their communities, they had little incentive to leave. A free transfer to only preferred worlds certainly wasn't going to motivate them.
As for going to the server. Many people were entirely unaware. I used to be on Balmung myself; transferring three days after my free trial ran out because I had friends on the server who sold me on the game and roleplaying. They, themselves, were also relatively new and simply went to Balmung because it had been deemed the unofficial RP server. I wager most players had similar experiences to me. Meanwhile, FFXIV's closest competitor avoided this problem by actually locking overcrowded servers and not taking extra money to get around it.
People blame the product because the product is at fault. You can't ignore a problem for almost four years than point the finger at the playerbase for not fixing the very problem you created.