This all goes back to the misunderstandings that were created between Manav and Archana, Manav thinking his marriage to Archana was over decided to take over Sachin's responsibilities and marry Shravani for the sake of her reputation and child. Then the misunderstandings between Archana and Manav were cleared, but it came too late because Manav already made the decision to marry Shravani. I know Archana and Manav are still married, but at the time Manav made this decision he and Archana signed divorce papers.
I get the frustration with Manav though, his divorce from Archana has not been finalized yet all these things are happening with him and Shravani and it is unfair to Archana. Manav feels obligated to Shravani but in reality he owes her nothing. Shravani got pregnant for Sachin and was to marry him, Manav should not feel obligated towards her at all.
The thing I love about Manav and Archana is the fact they always think of others and their happiness, but it is also the thing I hate about them because they are willing to suffer themselves in the process.