the deal was supposed to have a broad consensus. if congress feels that bjp is a party of devil and has to be opposed at all costs - that also meant cozying up with left - just to keep "communal forces away".
serves them right if they have that kind of hatred for bjp, heck - they even closed a great golden quadrilateral project, which is more important than the nuclear deal.
what does congress expect from bjp, with the kind of dirty politics they have played