I'm only going by memory so I could be wrong, but I think those licenses went to whomever applied for them first back in the early days of radio. Someone will surely be along to confirm or correct me on that.
Everyone who applied early (1922 or before) started on equal footing - 100 watts or less on one or two shared frequencies.
By the time higher power operation started to become a thing in late 1923-1924, there still weren't the class designations. It was sort of first come first served for stations that wanted to go to 5000 watts or more.
To some extent, the owners that were most engaged in developing the engineering for high power were able to get priority for those licenses, which certainly explains WGY, WLW, RCA's WEAF and WJZ.
It wasn't until General Order 40 in 1928 that the current allocation scheme really took form. Even then, 5000 watts was "high power" for stations like WHAM. There was lots of shuffling of allocations as stations were pushed into share-time and synchronous situations (WBBM/KFAB on 770, WJZ/WBAL/WTIC on 760) and as politicians bickered over the distribution of high power allocations among the various radio districts. That's why Chicago lost a high power allocation as KYW moved to Philadelphia in 1934.
Anyway, it wasn't just Eastman (who founded Kodak, not Polaroid!!!) and his pull that got WHAM to 50,000 watts, and in any event he had sold the station in 1927 and died in 1931.
Some of it was that Rochester was in fact a pretty large city in the 1930s, some of it was Stromberg Carlson's engineering and political pull, and some of it was that Rochester was in a different radio region from downstate NY and so WHAM had less competition for an available class I allocation. Buffalo, which was and is a bigger city, had low-dial 5 kW allocations for WGR and WBEN that Rochester lacked, and had some political issues with the market domination of one company that would have been exacerbated by a I-A grant.
It's unlikely Rochester would have merited a I-A allocation if they'd been handing them out in the 1950s or later, but from the vantage point of the 1928-1934 era when those allocations were being made, it made a lot of sense - especially when you consider the additional population WHAM served across central and western NY in places like Elmira and Ithaca that didn't yet have their own stations.