Its probably not the reason they are attacking (except in as much that it makes the iranian regime vulnerable). However i would say that yes, humanitarian intervention is one of the only non self-defense justifications for war that anyone has ever accepted in the post-ww2 era. (Edit: to clarify, im saying its the type of thing people build justifications for war around. Whether its a valid justification on this specific case is probably highly debatable. I think a reasonable argument could be made)

The 'tens of thousands' figure is one primary justification. Iran (eventually) getting a nuke is another.