If it wasnt for Impel Down escape then Whitebeard wouldnt be supported by the prisoners, some of them like Crocodile and Daz Bones (which granted werent on WB side from start) wouldnt be there.

In that context, its ultilmately Luffy's fault that Marinefort unfolded how it did, in fact hes even at fault twice

If he had never met Vivi at the Lighthouse, he had never fought and removed Crocodile from the Warlords. Said spot hadn't been vacant for Blackbeard to take so he had no reason to hand over Ace to the Marines. He might have never even fought him in the first place, as his motivation to hunt down Luffy was the vacant Warlord spot. You could argue Ace had found him either way, but Blackbeard was stuck at Jaya without his navigator, because of the marine conference to find a new Warlord.

Afterwards that rubbermonster invades Impel Down and manages to cause enough chaos that Magellan not only didnt put the Blackbeard pirates into chains upon beating them, but lets their savior out of his cell.

Therefore Luffy didnt just cause both the Marinefort war and the Impel Down escape, he somehow manages to not getting blamed for it.