May be .Because traditionally Kerala is a communist influenced state.And so people choice was always LDF or UDF.Congress have Muslim IUML and Christians,at certain extent Mani group support .and that makes UDF stronger here.
But now it is a new generation.Older generation support Congress or Communist no matter what.But new gen youths is starting to support BJP including Muslims.
But BJP dont get much larger seats in near future.The main reason is that minority status in Kerala is balanced i other words the real minority in Kerala is Hindus .Together Muslims and Christians are outnumbering Hindus.