Sure there is!
Losing half your teams - they're merging two separate leagues, and are able to get started with the strongest markets/franchises
Third of your TV partners - NBC was a bit player. ABC/ESPN and FOX were the major partners of the USFL and XFL respectively, and will continue to be major partners moving forward
Entire western half of the map - they want to get started in a more concentrated geographic area in order to ease travel and create better rivalries
Loosing both brand names - they want to move forward with a new brandname that fans of both leagues can get behind, and not look like one of the former leagues "won"
Look - history does suggest that the odds are against a new spring league (since both USFL and XFL had two separate goes at it, and failed all 4 times). I certainly wouldn't bet on the UFL succeeding. But there is a core nugget of what seems like a good idea - that Americans love foorball, but it's only played a short time of the year (September to January), so there's a market to watch foorball in the spring. If you can keep costs under control and moderate expectations maybe it can work.
The merger is happening because both individual leagues did significantly worse than the money behind them expected them to. The teams that are being folded are being folded because no venue, anywhere, wants them. NBC is not a bit player, they're a far bigger and more successful broadcaster than Fox.
They invested time and money in the thrice-failed XFL and twice-failed USFL brands, only to settle on the twice-failed UFL brand that they had to pry out of the hands of a literal conman.
There is not a demand for football in general. There's a demand for the NFL because it's the best football in the world and there's a demand for college football because of geography, tradition, and high enrollments. This league's pitch is "we're just like the NFL, except drastically worse in every respect". There is nothing the UFL is doing better than the USFL 1.0, WLAF/NFL Europe, CFL USA, XFL 1.0, UFL, AAF, XFL 2.0, USFL 2.0, or XFL 3.0. There is no reason to expect better results.
They are rearranging deck chairs on the Titanic. The viewership numbers have been trending downwards since XFL 2.0's first season and there's no reason to expect they'll improve with major markets like Philadelphia, NY/NJ, Pittsburgh, Orlando, Vegas, and Seattle gone.