Unfortunately for him, the back-then Prime Minister, Renzi, decided to drop support for him, pushed by many interest groups (some say even the roman mafia), angry at Marino for wanting to disrupt old balances of power.
A pity. He would have done great things for Rome.
For example - he made up a ridiculous story about being invited by the pope to attend a march in Philadelphia, which quickly got exposed as a lie. He was also completely unable to handle the local Roman political players / senior civil servants (who, granted, are hideously corrupt and have been running things for their own self dealings with left governments, center governments, far right governments, and 5 star governments (whatever they are)).
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.
I am roughly in agreement with your longer explanation. And, by the way: thanks for your work with his campaign; I wish he stayed and enacted these reforms.
Suburra is also the name of an area in ancient Rome of lower class criminals and prostitution.