As of yet, there is no credible explanation, but one thing i think Oda might do, is use the 20years prophecy to explain why Ace preferred waiting for the right time. The last time he saw Tama, he promised her to come back with a bigger crew and free Wano(turning it into a place she could eat as much as she wants)
And since he encountered Yamato and they ended up friends, she probably talked him about the prophecy, and even Oden's journal
Which could have been the trigger to convince him to come back at a more suitable time. He probably talked about Luffy as well considering Yamato said she had been waiting for him for a long time.
Up to Oda to cover this plothole or not
![](https://i.imgur.com/TgxNQuq.png)
![](https://i.imgur.com/6oOyWAh.png)
And since he encountered Yamato and they ended up friends, she probably talked him about the prophecy, and even Oden's journal
![](https://i.imgur.com/418SPAk.png)
Which could have been the trigger to convince him to come back at a more suitable time. He probably talked about Luffy as well considering Yamato said she had been waiting for him for a long time.
Up to Oda to cover this plothole or not