It never made sense in the first place. The World Government have always been the Big Bad and since long before Blackbeard entered the picture. Whitebeard basically told Blackbeard that he ain't that guy. That after his downfall, there would be an even bigger battle.
Whitebeard told him he is not the guy that Roger waits. BB is the guy that inherited Xebec's will, not Roger's.
Xebec's will is to be the king of the world. Roger's will is different.
Imu literally showed nothing to handle Luffy's Nika DF powers. Shirahoshi is an ancient weapon can do the same to an island, that doesn't make her powerful in 1 v 1.
BB on the otherhand has
the only power to nullify Nika's DF power in 1 v 1. Not Imu.
We don't even know how that Sky AoE works, for sure Imu would delete Blackbeard's or Big mom's islands if it was easy, even if not for Kaido's island due to Wano's importance, Blackbeard and Big mom's island werent important for them.
They couldn't do shit to Laugh Tale as well.
This AoE happened to a World Government county. Its in doubt that they can do it to a non-WG country for some reason. If it happens to a non-WG country then its a huge AoE but still useless in 1 v 1.
How you trolls thinking Luffy vs. Imu will happen on Marijoa? You think Imu will try to destroy Marijoa from sky alongwith everything includes the island?
Imu is still featless in terms of 1 v 1 combat, and has no ability to handle Nika DF, only BB has that.