Bowser's been simping for Peach since Super Mario RPG, and even earlier in the expanded lore.

And, having just came from watching the movie, if she'd gone and gotten the Kongs' help on her own, she probably would have beaten DK, but then Bowser would still have beaten their army just like he did here, and she would have ended up overwhelmed when Bowser launched the Banzai Bill without Mario and DK there to make the save.