I'm with you Giordano!
It is naive to believe that a universal flood happened in historical time. The flood is an almost universal myth based on the climate change events at the end of the last ice age which happened during the late Upper Palaeolithic period of human prehistory. (Late Old Stone Age)
Up until 14,000 years ago much of the atmospheric moisture was bound up in greatly enlarged polar ice-mass which made the weather much drier and colder than now, and much lower sea levels existed as a consequence. As the ice melted it freed up the water which conspicuously fell as heavy rain and the sea rose as much as 100 meters to modern levels. I think it very likely that these events gave birth to the flood myths including Noah's.
The Biblical take on things was clearly for the purpose of controlling people; to threaten those who would disobey god and praise and reward those who toe the line fearing to displease the tyrant God. Death or reward is a primitive inducement!
Noah, like Adam and Eve, never existed so the question of whether he preached or not is actually irrelevant to reality.
It’s a disastrous intellectual investment to imagine that was it says in the Bible is true.