Oda didn't even feel that it was right that Kidd & Law alone defeated BM so he conveniently made some new "plot" nukes out of thin air to make the events more believable lol.
That and she forgot to use ACoC, kept turning her back on them. A lot of weird shit was happening during that fight.
If anything, Law withholding R-Room the entire fight. The biggest Plot convenience we saw. He legitimately had the ability to stop homie fusion/healing/ an overall control of The ability. Literally waits until the final seconds of the fight to make use of it. An the kickers, he only use it to shut meme up.