The day the rishta came, Sanchi was busy begging him "don't leave me Jagdish, or I'll die"...DS threatened him not to do anything which hurts Anandi's happiness, he told the Singhs I want to speak with Anandi, he looked at the Shekars and asked if they they thought this over, SUmitra, DS everyone warned Jagya not to do anything which will burden Anandi. He thought Anandi is there, she must be endorsing this rishta, his family also felt the same thing so he agreed to it. Sumitra fell in love with Sanchi immediately...
Basically everything was done quickly and in haste in order to create drama, even his breaking off the rishta which rly pushed TRPs up was all done to create lots of drama.