Spanos is second fiddle to anyone in LA, Rams or Raiders. Kroenke isn't just writing a 2 billion dollar check, but he's got the money, and he has the money to invest in the city, and he doesn't need any help from the NFL, nothing like that. Spanos can borrow money to build a stadium, but he can invest the type of money Kroenke can into the market to really make the idea work.
Again, Raiders or Rams, the Chargers are second fiddle at best. The big difference is that in Carson he's going to pay more to be that second fiddle.. He'll get more returns, but no matter what he'll be the owner of the other LA team.
There was word a while back about the NFL would rather keep San Diego if possible because they want to put Super Bowls there again in a top stadium (it really is a beautiful city)... Plus it gives them more options for Super Bowls, they love Super Bowls in warm weather areas.
They also have more operating costs in Carson (about 300K a year for the gas vents)... It's not that they'll go broke (although an article said it'll take about 30-40 years for Carson to be operating in the green) but that is less money to invest into the market. Having a brand new stadium is only part of the equation.
I think that Carson is a viable project, and the NFL would happily select it.. I maintain Inglewood is the better project in pretty much every category, but Carson is a doable project as well.