i'm not sure if i've been over this in this space...
why does putin keep winning elections? the western narrative is that he rigs them. but, this is a poor understanding of things, and only works if you're ignorant of what's happening there and has been happening there for the last several decades.
westerners are used to very narrow political spectrums. you can vote for the left bourgeois party or the right bourgeois party. there might be a fake socialist party, or maybe some puppets of capital pretending to be libertarians. but, it's all strictly in a tiny sphere of neo-liberalism.
russia has a massive political spectrum. the options are communists, capitalists and fascists. putin's party is neither liberal nor conservative in western terms, but a broad capitalist liberal-conservative front against the commies on their left and the fascists on their right.
the main opposition party in russia is still the communist party. no other party has overtaken it. there is a very small movement towards social democracy, but the force most likely to threaten putin at this moment is a right-wing nationalism led by the likes of navalny.
this is why putin and his party are unassailable: the other options are literally soviets and fascists. literally. and, if the vote ever split, the communists would almost certainly win.