I think the reason Daymare town is abandoned is because of its ruler. Maybe the reason they have technology and well built towns is because of the first ruler, who was fair and helped the daymare town kingdom (dont know what else to call it) grow. But soon the king died and another ruler or relative took over. He kept the wealth to himself, and let everything else fall into poverty and squalor. This also explains why you have bad things (abandonment, disrepair, maltreatment) along with others (money, complex mechanics). In the seaweed fossil chasm (dmt 4) there is a building with a painting of a man that says under it "big daddy, the king". This could be first king or the second one. Also, at the end of dmt 4 The player enters a giant city which shows none of the disrepair like in the others. This might be the kings palace/city, as he is using all the money on it than the rest of the kingdom.