This is possible , Dalits may have not taken much interest in this elections.
All is left for Yadavs and other backward castes
Since its still the SP govt. the SP leaders would have provided quid pro quo rewards to local community leaders for their vote. The average UP voter is quite politically mature and would have milked it for all its worth.
I do not think the BJP was really looking to win these by-elections seats. They would be focused on the next elections and in all probability is preparing ground for that. The SP OTOH knows that it might not form the govt. next time so will go out at all strenght to make this rule as stable and strong as possible.
BSP remains a mystery.