I haven't seen the serial from the start. So, I'm not sure ... but I read or saw somewhere that everyone's marriage in the family is a love marriage except Ishan's. So I believe that Eshwar-Shailaja too had a love marriage.
In the parting letter Eshwar mentions that he doesn't love Shailaja any more and her presence or absence does not matter to him since he loves Meera and cant live without her. It makes me think that may be Eshwar never loved Shailaja in the first place and she was perhaps just an infatuation or fascination for him. So his failure to understand his own heart proved to be very dreadful for Shailaja. She had to pay a price for his immaturity and erred decisions ..... this is not done, not acceptable at all! Eshwar is at fault here.
Like Dadaji says, Eshwar cant be forgiven for deserting his own kids. Which father on earth will give a choice to the mother that if she is not willing to take the responsibilities of their kids then he will make arrangements for them! He is such an unloving, uncaring, irresponsible and mean father. Once again he is at fault here.
He breaks ties with his own parents and siblings who have loved him, cared for him all along! Well well ..... what a selfish and an opportunistic guy!
The only good thing he did is that he didn't keep Shailaja in the dark and confessed all his feelings to her. But this does not make up for all the bad things he has done. He ruined Shailaja's and his kids life for no fault of theirs. He might have found true love (which I doubt! Career-minded that he is, he must have married Meera just for green card sake!) but his bad deeds will come back to him one day!