The F-650 weight limit is 50,000lbs (including trailer) off the factory floor.
However it’s common to spend a hundred grand on modifications, and those can easily include suspension and braking upgrades which would allow higher weight limits (especially trailer weight, where almost none of the weight is actually on the truck itself).
If you need to tow a crane or something like that, this is a perfect truck to use as a starting point. It’s small enough to drive off the highway to job sites in residential/etc areas, but capable enough (especially modified) to handle loads that would normally require a full size truck I that can’t possibly be reversed between two houses to get the crane into someone’s back yard where you need it.
Europe has trucks like this too. They just aren’t from a culturally popular brand like Ford.