literally everyone could have done something
Kid and crew have no connection to Momo.
Law is indifferent since Shinobu doubted the loyalty of his crew to the alliance.
Luffy and co. were far away and knew of Kanjuro betrayal after he kidnapped Momo.
Usopp could not snipe because the cloud blocked his vision. Same with Robin.
Sanji returns to protect Nami and Robin from Arrows.
Zoro, Franky could have hurt Momo if they attack Kanjuro.
Only Nami could have done something but that could have impeded the ship's direction.