As I said, they tried and failed because nobody downloaded it. I'm not sure why you're suddenly bringing Epic's motives into a comment chain about the desirability of sideloading though? Epic is obviously looking to skirt store fees and doesn't actually prefer to run their own store, but that has nothing to do with anything above in the chain.
I don't think most people would. I think most sideloading would be by users making things that fall outside of what Apple allows on their store, like on Android. I see no coherent reason at all why things would be any different on iOS, and nobody has presented one here beyond just asserting the premise that it would be different, and I don't think "Epic believes it is" is a convincing argument.