User blog comment:PrettyGoodGamer/Who was the one that tipped the Queen Mama Chanter?/@comment-78.134.87.22-20200609104134

Given that in the anime, King actually kicks the Queen Chanter off the waterfall, I assume it was to point out how much Marco and King are "foils" to each other. As for King and Marco being the same person in disguise, I think that's too much of a stretch, King's flames are clearly different from Marco's flames, not to mention their size and all.