I can sort of, kind of understand why Hollywood didn't use Ethel Merman in the feature film. Why, though, she wasn't hired for the TV production, I have no idea. Perhaps she had another commitment, but given that television waited 11 years to do the show, it would seem that waiting a bit longer until she could do the production wouldn't have been the biggest challenge in the world. So, it probably wasn't that. Perhaps it was because Mary Martin had toured the country with the show, and network executives thought she'd be more familiar to them. Perhaps they thought her more low-key style would fit the small screen better (though larger-than-large personalities certainly weren't a problem in the early days of TV.) Maybe it was because Mary Martin had had great live-TV success with a musical previously, having done Peter Pan in 1955 and 1956. It was likely a combination of the above reasons -- or something else.
Still, it must have been hard on Ethel Merman to have been passed by twice. Whether it was more difficult or eased the pain a bit that she and Mary Martin were close friends, it would be interesting to know. That they stayed friends for may decades to follow at least showed that no wall lingered. Hey, in the end, as this show noted, there's no business like show business.
Anyway, we had a video of Ethel Merman in a late-revival of the show. But how about seeing Mary Martin in the role?! As you might imagine, this is a rare clip from that 1957 production. Here she is singing, "You Can’t Get a Man with a Gun."