Let's not forget, Oda embarrassed and dehyped the villain behind an entire saga, in the middle of his own arc, before the fighting even started. For Oden of all people. Not just a dead flashback character, but an underling dead flashback character, not even a top guy.
When Oda has a choice between the dead flashback character and an upcoming villain who can use the hype, not only does he choose the dead character, he does it in embarrassing fashion.
Garling's best bet was never running into Xebec, the outcome couldn't be more obvious (though how onesided it was is still pretty shocking).