Speaking specifically about Canon - they had one or two senior reps at a major sporting event. They were setting up cameras for specific sports or specific photographer needs. It gets very sport specific. For example, if Sony were to do that with the A9iii, they would have different focus modes and custom area modes, different configurations of the speed boost button, etc. The configuration for gymnastics is very different from boxing or swimming even though all are indoors. They would also configure remote cameras for placement at the bottom of a pool or hung from the rafters.Basically, those professional photographers are coming barehanded, have to pick up a factory reset body, set it all up, and be expected to shoot fluently?
I would assume there is communication beforehand about specific sports or setting requests. Most of the cameras and lenses are reserved in advance. A given pro might have four cameras and lenses, but at the Olympics might need more camera bodies or specific lenses. Canon and others also are there to provide on site service and repairs, sensor cleaning, etc.