We don’t even know what Admirals where thereit's less hype and more that he canonically is the only person to have ever freed slaves and attacked Mariejois. It was mentioned a bunch of times and is basically perfect flashback material. How the hell did he pull that off? How did the admirals not zap him? The only other time we've ever heard of celestial dragons and their slaves being in any danger was God Valley, so it was a pretty significant event and was weird that Oda glossed over it to show us something much less interesting
Kizaru, Aokiji, and Sakazuki were a bunch of Vice Admirals at the time
Sengoku and Garp were the ones active back then