There are probably thousands of reasons for the flood. But the mixing of DNA IMHO cannot be disputed per Genesis 6.
That has to be one of the major catalysts that caused God to react in Judgement.
Jesus The Christ warned us again that we’ll be living in the days like Noah - I think we are.
God created our DNA and used it / uses it as the carrier for information, the data to make you, the individual made in His image.When the Angels used human females to conceive their human-esque offspring they altered what God made for His use, into something stolen from God to do what they the fallen ones wanted to express as 'their creation'.
Somehow the DNA receives information from a coordinate system not confined to our sensed three of space and one of time. That 'greater / different coordinate system will not need DNA as we now know it to define the being we shall be made as / made to be when GOD makes a new greater capabilities body and behavior mechanism for us at the snatching away Departure known as The Rapture of the Body of Christ.
By snatching His away, He prevents the DNA of His creation from being altered into something bastardized by the 'other' deceiving, lying, lacking His Righteousness in the spirit fallen ones under satan's rule.
The evil one and his minions have polluted not just the Earth and all connected to it, they have polluted the First Heaven. THAT will be instantly cleansed by the Voice of the Archangel, BEFORE Our Righteous Lord enters that Heaven to command the Body of Crist deceased spirits to go to their new bodies and behavior mechanisms and we transformed also, to rise into the clouds to meet the Lord in the First Heaven.
I believe 'the last trump / Trumpet blast is similar to the last trumpet blast of the Shofar which set the tribes in motion to leave the encampment and travel en masse. The passage in 1 Thess 4 is hallmarked with three distinct events: the Shout, which is related to the calling up from the dead real physical bodies, albeit these bodies will be of a greater coordinate system fashion similar to how Jesus is now (1 John 3:2). These newly fashioned bodies are no longer 'in' the polluted coordinate system we now sense so therighteous spirits are instantly united to their new bodies in resurrection to a coordinate system not polluted. The second aspect is the Voice of the Archangel, causing the spirits of the living body of Christ to resonate with the Shout, kind of like an echo, transforming all the alive members of the Body of Christ into the greater coordinate system bodies and souls fit for eternal habitation. Then the Trumpet sounds and we all, all the members since the Peter preaching on the Day of Pentecost when the Spirit was promised ti abide in the human spirit of believers, all the Body (think collectively of the individual members of the 'student body') is caught up and returns with Jesus to The Father's House.