here's a wild guess….clown got no haki, and he cannot infuse haki in ice (in which, of all things, he chose icicle to stab a snow woman)...it doesnt matter if monet can activate her intangibilty automatically,...maybe the only reason clown can hold monet's heart is because of the box law creates to hold the heart, maybe monet does get hurt when her got stabbed...but i really dont it would kill her.
unless infused his weapon with haki....
maybe this is a weak example, but nico robin (without haki) smashed monet but monet reassembled herself.
and vergo will survive too i believe, no explosion happened....
either way, doflamingo will fetch them.
we might be disappointed when doflamingo just flies above the strawhats/law/smoker in the trolley and just gives them the "death stare" and then goes directly to save the two.