One of the dark features of Indian democracy is the eligibility of candidates with criminal records to contest in the general election. So far each ruling party, irrespective of whichever party formed the government, had a certain number of such criminals. That is because these criminals possess winnable characteristics over honest candidates during the contest. They are very shrewd and extremely cunning mastering the art of befooling the voters by doling out some crumbs of benefit to them.
Seeing from that angle it is the fault of the voters to elect them in the first place. But they too see their petty personal benefit in preference to the national interest. The case of of notorious Veerappan is an example in point. He used to keep the villagers happy in ways they liked it and they in return protected him.
This wrong practice can only be stopped by enacting a law disqualifying the criminals to contest. No political party showed any interest in doing away with it so far.
It can be possible by a massive upheaval of public protest. That is not in sight yet. So, continue to be ruled by criminals.