People did not vote Congress for "secularism and universalism". Most voters are not educated enough to bother about such things like political leanings and philosophies, their only outlook in choosing who to vote is their perception of what the candidate is bringing to the table for them at a local level. A lot of India's voter base does not have affiliations with "Left" or "Right" politics as we know it, and it's rather easily swayed by intelligent and targeted marketing campaigns.

BJP/NDA simply outclasses every other force in terms of its outreach and marketing prowess, and with the kind of control it now has over mainstream media, challenging them will be a herculean task at least for the time being (and filled with a very tangible risk of self-destruction).