Noah's people were drowned because they belied him 25:37-40
25:37 The nation of Noah, We drowned them when they belied their Messenger, and made of them a sign to the nation. For the harm doers We have prepared a painful punishment
25:40 They have surely passed by the village which was rained upon by evil rain (of stones); what, have they never seen it? No, they look for no resurrection.