When Lenin said “Politics is concentrated economics” what does it mean how do we understand it?

The superstructure Political, juridical, philosophical, religious, literary, artistic, etc the very function of these ‘non-economic’ institutions means that they have enormous economic impact. They are concerned with controlling the base, with fixing existing relations of exploitation, and therefore in putting a limit on changes in the relations of production, even if this also involves stopping further development of the productive forces.
The way the political and judicial feed back into the economic is absolutely central to Marx’s whole approach. It is this alone which enables him to talk of successive, distinct ‘modes of production’ — stages in history in which the organisation of production and exploitation is frozen in certain ways, each with its distinctive ruling class seeking to mould the whole of society to fit in with its requirements.
Because of the activity of the ‘superstructure’ in trying to stop new forms of production and exploitation that challenge the monopoly of wealth and power of the old ruling class. Its laws declare the new ways to be illegal. Its religious institutions denounce them as immoral. Its police use torture against them. Its armies sack towns where they are practised.
The superstructure always attempts to freezing the existing production relations so that the monopoly of wealth and power of the old ruling class remains intact.
‘The history of all hitherto existing society is the history of class struggle’, wrote Marx and Engels at the beginning of The Communist Manifesto. But the class struggle is precisely the struggle between those who use the political and ideological institutions of the superstructure to maintain their power over the productive ‘base’ and exploitation, and those who put up resistance to them.
Revolutionary reconstitution of the society cannot take place without massive political and ideological struggles. It is these which determine whether one set of social activities (those of the superstructure) cramp a different set of social activities (those involved in maintaining and developing the material base). It is these which decide, for Marx, whether the existing ruling class maintains its power until it ruins society, or whether a rising class, based on new forms of production, displaces it.
The superstructure exists to defend exploitation and its fruits. Any real fight against the existing structures of exploitation becomes a fight against the superstructure, a political fight. As Lenin put it, ‘Politics is concentrated economics.’

In a nutshell without a massive political and ideological struggle in the superstructure it is simply impossible to crush the existing capitalist order.