Sin has a way of becoming more and more sinful, doesn't it? The more you toy with it, the more your heart is hardened in the direction of giving yourself over to more and more sin, and this ultimately spills over into more heinous sins, which mount up an increase of greater condemnation and judgment in the end. The progression of sin to the point that even every thought and intention of the heart of mankind was continually wicked, during the time of Noah, was not something that came about in a short period of time. And Sodom and Gomorrah didn't become "Sodom and Gomorrah" over night. No, these kinds of utter moral collapses came gradually, over time, as God (as a form of judgment) had progressively delivered unrepentant, wicked men and women over to their own natural inclinations, leading them to commit all kinds of gross atrocities, to the point that their later destruction was all the more increased, intensified and final.