What the fuck does that have to do with what I said lerkan.
Why didn't the MARINES bring up mihawk MARINE hunting in the past.
This is an essential in nearly the entire history of storytelling.
Why did character x not bring up point y sooner?
You find this in every story ever.
But if you want a actual answer to your specific question:
I suggest you read back when Krieg was a thing and realize he called himself Admiral and sailed with a stolen navy ship
Your issue is less about the marines as much as it is about being told to you.
And the simplest point is:
Mihawk is a very isolated character. Loner by default. Not very sociable.
You aint gonna get anything worth out of him.
That leaves other characters to mention that detail and that means they need a legitimate reason to bring it up.
And its such a nothingburger that there is no reason of importance to squash this in somewhere where it doesnt belong. Its no explosive plot point, its no Nika revelation. Its nothing that couldnt wait to be revealed.
Hence we got it the way we did.
And if you wanna draw comparisons to Zoro, he is literally a main character whos endgoal is Mihawk. We actually needed to learn about him.
Mihawk and actual info about him was always gonna be saved for the end because its Zoros endgoal, I dont know what you are expecting.
Same reason we arent really told much about BB and his crew or the Red Hair Pirates, they are endgame material just like Mihawk.
You find this everywhere.
Shounen specifics are Bleach with Yamamoto. Naruto with Madara.
End game material is where the good stuff comed out.