Imagine him coming out after he declared he was dead..
Only one thing is important to DM and that is his ego and name in society.. and how people percieve him.. If DM had given in to Moti then he would have been seen as weak..
Plus he was angry at Moti at the fact that she put the LOC in the house.. so obv he wasn't coming out..
No matter what though he would chose Moti over Santu.. If Santu raised her voice before Moti or said something to hurt Moti even if it was Moti's fault i am 10001% sure he will find Santu responsible..cos that's just him..
No matter how hard he tries he can NOT be angry or upset at Moti.. When Moti hid the raaz about Maulik i don't think DM punished her..
Do you remember the episode when Maulik asked why his mother was being punished?? he said its not punishment instead he wanted his sister to sort out the problems so that they could be proper parents.. so i don't see how you are saying that DM would support Santu and not Moti..