I hope the new USFL whenever it starts has learned from the old USFL as far as the mistakes that the old league made. Like having clubs in established NFL markets and having to compete with the NFL which was already the number one pro sports league in America at this point for fans and fan support. And to make that problem worst, the USFL decided that they were going to play in the fall after the 1985 season and not only try to compete with the NFL for fans, but try to compete with them the same time of year. Which of course didn't happen since the USFL went out of business following the 1985 season.
Another key mistake being that they expanded not only in NFL markets, but expanded way too fast. Going from 10-12 clubs in 1983 to 18 by 1985. Which is way too fast and they were at least ten years away from successfully being able to support that many franchises. Especially since they were competing with the NFL for the exact same fans. And of course some of the questionable management groups like Donald Trump in New York just to name one who perhaps has the most responsibility for why the USFL folded after the 1985 season.
What the USFL did real well was signing players and a lot of them could've either been drafted and done very in the NFL like Herschel Walker and Steve Young. Or had previously played and done well in the NFL like Brian Sipe and Doug Williams. Which is what they would be able to do again especially if they get a player sharing agreement with the NFL and the NFL allows for them to borrow some of their inexperienced players for their league. Don't expand so fast, stay out of the NFL markets, and play in the spring and summer and the USFL could do real well in the future.