It’s literally the largest media market in the country. The more fan interest the league can generate in that market, the better.
The Giants are a multi-time SB champion and both they and the Jets are long time fixtures with generations of loyal fans; the same can’t be said about the Rams or Chargers even despite the Rams once residing there.
They don’t want L.A. to be a passive market; they want it to become a rabid market like it has in other places.