I think this narrative has spread too much and has become one of those lies that repeated indefinitely become truths.
Marino had a problem: he wasn't a long time memmber of PD (Democratic Party) of Rome, they had another candidate but Marino beat him at the primaries and became mayor of Rome.
So they started the war against him.
Renzi simply acknowledged that the roman PD was a nest of vipers and put a commissar (Orfini) to handle the transition.
But it wasn't Renzi that created Mafia capitale where members of PD were involved with bipartisan criminals of Rome (like Tassoni in Ostia that was in bed with the gipsy-mob family Spada)
I'm also talking about corruption, years after it's clear that Renzi was right when che tried to reset the roman PD, his fault was not being able to actually clean the house
https://roma.repubblica.it/cronaca/2021/04/10/news/scandalo_...
(sorry, Italian only)
Also, Marino wasn't loved by romans because he had radicals ideas about modernizing the city and romans are generally resistant to changes and also because he made some bad communication mistake.
I'm telling this as a roman who campaigned for Marino, voted for him and was happy having him as mayor.