I've driven 2 models of an Italian brand, my previous car had the gas tank on the passenger side, and my current one has it on the driver side. I do wonder why they changed it.
There's also the issue of pulling to a small road side petrol station, having the fuel door on the passenger side means you don't have to be standing next to the busy road while refuelling.
Depending on model years, it could have something to do with Fiat merging with Chrysler in 2014. European brands usually have them on the passenger's side, while US brands have them on the driver's side. Maybe that new Fiat was designed in the US.
"... many European cars have the fuel door located on the passenger side, while many Japanese and American vehicles have the fuel door on the driver side. Both techniques have valid reasons. European automakers place the fuel filler on the passenger side for the sake of safety when a vehicle has run out of fuel and has pulled off onto the shoulder of the road to fill up from a canister. Meanwhile, American OEMs tend to place the fuel door on the driver side of the vehicle for convenience reasons, so that a driver doesn't have to walk around the vehicle when filling up at a gas station."[0]
Brings to mind the Dead Kennedys album name, "Give Me Convenience or Give Me Death"[0] https://fordauthority.com/2020/08/ford-designer-credited-for...
The fuel side indicator is quite helpful to me.