After independence, India adopted the way of Socialist democracy, modelled along Soviet principles. And for five decades since independence, India was more or less firmly in the grip of the old Left, which, since Indira Gandhi’s Emergency lost its legitimacy but continued in power due to the sheer inertia of the system until the alternate political ideology in the form of Nationalist Hindutva became popular.
But the thing is, the old Left defeated itself to a large extent much before Hindutva politics became mainstream and only the weaker shell of the old Left was cleaned up by the BJP in recent times.
The strange part is that, adharmic Leftism of the old school faced a different facet of adharma which slowed down the Leftist progress considerably: massive corruption and red-tape bureaucracy exemplified by the infamous License Raj. An efficient and non-corrupt Leftism would have resulted in a headlong dive into far Left politics for India, but the sheer corruption of the old Left system disillusioned the people and led to the formation of alternative politics (though still not true right wing, considerably less Left than the Socialism of old). A truly efficient Leftism in India after independence would have led to far more brutal and tyrannical License Raj and a lot more Leftist repression.
For Dharma to prevail over an increasingly cohesive, destructive adharma, either a Dharmic Hero of considerable power needs to be born to destroy that adharma, or, if the conditions for such a Dharmic Hero to be born are not satisfied, the adharma needs to be slowed down considerably in order not to do too much damage, either through internal conflicts/contradictions to reduce its cohesion or through an external opposing adharmic force.
I see this adharma vs adharma as a kind of Dharmic reaction to slow down or destroy the more evil adharma before it can do too much harm. Notice how the idealistic Nehruvian vision of a Socialist utopia ultimately degraded into petty dynastic politics within decades. Even though Indians have suffered under the corruption of this highly inefficient and weakened Leftism, still this suffering is nothing compared to the catastrophe that would have occurred if the Leftist programme had been fully realized in India.
Instead, today, though institutional corruption thrives to a considerable extent (and which needs to be addressed by Dharmic forces), the old Left is all but defeated, completely discredited and dispirited, while the new Left (progressivism) is still at an early stage of development in India.
In history we find such examples of adharmic forces being slowed down by adharmic forces with opposing goals or even the sheer inefficiencies of the system in which Leftism thrives. An adharmic Hitler whose destructiveness became too much for the Dharmic to bear, faced an opposing adharmic Stalin who checked his progress and eventually destroyed him. The best part is that Dharma ensures that even the victorious adharmic force in the struggle is considerably weakened.
Even in our puranas, we find that Asuras or Rakshasas, who became extraordinarily powerful through tapas and extraordinarily repressive towards the virtuous, were defeated and destroyed not just by the Lord incarnating as an Avatara Purusha but also by their own weaknesses, internal contradictions and egotism.
Dharma always provides a solution to the Dharmic though that solution may not be immediately obvious or yield immediate results.