A bunch of poor people, who grew up on hunted and locally grown seasonal foods, where sugar and fat were expensive commodities, suddenly had cheap access to the (literal) fruits of imperialism and about a decade of government bolstering domestic industrial infrastructure on the cheap. Actually this is more of a 1930s-1940s thing that just culminated in a 1950s thing.

You spent your whole life eating backyard root vegetables stored in a dirt hole. Now you can go buy pineapples and bananas and coconuts, plus all the cream, cheese, sugars, and syrups you could. Nothing goes bad as quickly anymore because mass produced shelf-stable foods are new. Jello wasn’t something that took hours making anymore from scratch, you can go buy a cheap box of dried gelatin with flavor added. Mayo came from jars, not making emulsions at home. You can buy a lot of things pre-made and they’ll last longer than what you could make from scratch.

So from that you get mayonaise jello spam pies and banana ham suffles with syrup. People were trying everything they could. Their tastebuds were just amazed by salt and sugar.