Originally Posted by Chalmers3716

There can always be an anomoly-whether it's because Marriott hasn't succeeded there in the past, or they have difficulty with property owners/managers, or even just the city tending to have a higher concentration of independent properties. None of that changes the fact that by and large, Marriott's footprint is massive.

It's worth noting, the article you cite, lists the next largest chains as well. Here's how they stack up in Rome:

Hilton-8 hotels
Accor-13 hotels
Best Western-21 hotels
Wyndham-1 hotel

So, on average, they're a touch smaller than Marriott.
But, looking a bit closer....the furthest Marriott is 7.6 miles from the city center. Using that same metric, Accor drops down to....7 hotels. Best Western drops down to 14.

Other large chains: Hyatt-7 properties; Choice-6 properties; IHG-5 properties

So really, it seems that the takeaway here is, Rome has a lot of smaller brands or independents, but within the realm of loyalty programs, Marriott is still one of the best represented.