The economy of India was till recently and to some extent even now is controlled by the state, often arbitrarily.
Anyone wanting to start a business or run an industry or e gainfully self-employed had to seek state patronage in the form of licences and permits as will as protection from official harassment.
Politicians of a sort found a lucrative opportunity in brokering that state patronage. Not for them the areas of politics that deals with the genuine needs and interests of the populace.
Brokering state patronage by necessity creates a set of favourites around a politician: permits are awarded to such people irrespective of merit, even as illegal activities are allowed to flourish by keeping the police clear of them.
Official authority is misused in both cases. And once such corrupt practices mar the political field the way is clear for the entry of criminals.
To buy votes, to force people to vote for a certain person or party, to ensure the victory of a certain candidate, to terrorise opposition to submission the unscrupulous politician engages gangsters and gonads gradually, these criminals themselves enter out legislatures legitimately democratically and make the law of the land.
Misuse of state power and criminalisation of politics can be reduced and eliminated only if people participate on a larger scale in running the affairs of the state.
Power must be decentralised, rules and regulations must be transparent and there must be greater involvement of people in the government running through citizens committees, co-operatives, etc. The state must not interfere in each and every economic activity.