>>281312550
I think you're probably onto something. Xebec killed an admiral. Kong specifically wanted Garp on God Valley and Garp ended up being the hero of the marines. It's clear he was stronger than any admiral back then.

He then went onto train vice admiral Aokiji. It could be that after the death of the admiral and the realization that Garp was the the strongest, they copied some of his training methods into their program such as "no haki while training" and developed a stronger marineforce then they had back then, and now the admirals are physically stronger too.