Spoilers: it is definitely Luffy.
It was a counter claim to Zoro carrying Luffy, there is more evidence to Luffy carrying the team by being the main damage dealer, agro target, having the best mobility and field presence in general. And the prediction that losing G4 Luffy will lead to a stall war until he is back with the SNs unable to do that much without him.
Rifle put Kaido on the back foot, upon which Kid directly followed up while Kaido was craned back, this subsequently let Law and Killer do their attacks in a chain, so yes credit is due to all of them, but Luffy set up the chain.
If Zoro and the SNs tanked Mom's Lightning, Luffy is tanking prometheus, considering he already tanked the more powerful boro breath so not false.
The others weren't fucking attacked until the lightning blasts, how can you be saved if you weren't attacked? The lightning attacks are too fast to save someone from anyway...
Luffy's time limit is decided on entirely by Oda, when he wants to flip the switch, Luffy has shown the ability to come out of G4 earlier in this arc and yet over extended himself here for plot drama, if gattling hasn't done major damage then Luffy should have transformed back and regrouped, pure PIS.