How would any of the factions know to even come to egghead and make it there in time?
Only Blackbeard was already on the way if i remember correctly.
There are decent plot-reasons for each of these ones IMO:
- Grand Fleet has Luffy's vivre card and he literally died in Wano for a bit. So they've got a decent reason.
- The New MADS formed out of shared hatred for Vegapunk, so they have an comedic reason to run into more crap.
- Dragon is chasing Kuma.
- Shanks protects the weak in his territory, and Elbaf isn't far from that area. So if the warship attacked the civilians near his water, he'd have a reason to save them and could find out about the situation.
- Blackbeard's ship pulled up a while ago, so they're definitely around.
But there are also reasons not to be any of em:
- Grand Fleet is supposed to wait for Luffy's call.
- New MADS are cowardly types, so attacking a single warship is unlikely, let alone a buster call.
- Dragon seemed like he was way behind Kuma who just arrived.
- Shanks just finished smacking Kidd and wasn't sailing.
- BB pirates helping civilians against a warship is out of character.