> The only question is: why is Tesla seemingly giving up this "moat"?
Right now only about 2% of US new car sales are electric. In that small pond Tesla is the big fish, with something like 90% of that market. In the overall new car market, though, Tesla is a guppy.
Over the next decade or two, that overall market is likely to become more and more electric, with at some point ICE cars becoming the niche product instead of the other way around.
Will Tesla be a big fish in that future US new car market? I wouldn't bet on it. They arguably currently have the best electric drivetrain, but they are not as good at many or most of the other aspects of a car. My guess is that the current big car companies can learn to make a great electric drivetrain faster than Tesla can learn to make a great everything else.
By opening their charger network before the other companies get a good non-Tesla charging solution widely deployed Tesla has a good chance of becoming the dominant charging network in that future market where as a car company they remain a niche player (probably with sports cars being their niche). And all those electric cars from all those other companies need charging, so if Tesla can dominate the charging market that could be very lucrative for them.