I don't remember if it was a church or a video in the church, but it was explained to me once.
In the past, before the flood, the world was much different. There was a thick layer of water that surrounded out planet. This blocked more of the
radiation from the sun. After the flood, there was less to block it, and this is why you see a rapid drop off of ages after that point.
Coincidentally, they also talked about dinosaurs being real, and the reason carbon dating is off is similar. The atmosphere was much different in the
past. They believed in 'e'volution, not 'E'volution. There was a lot of less restrictive ideas from them and the speakers they listened to.
It has been so long since I been there and I can't remember the details.
Once again, church and science don't have to be completely separate.
You could also argue, another reason was our continuing to sin is bad for us.
Another is, we are slowly devolving from out perfect creation over generations of muddying the blood ... through incest ... which created some bad
things in the OT.
Oh well, what can you do