I'm a big fan of this news! The Boston/DC corridor is the most densely populated band of the country, so this expansion has a high benefit:cost ratio. It also provides a core from which to build outward. It's instructive to look at how the railroads were built out in the 1880s, with the initial build focused on the northeast corridor, with strong westward links to Chicago, Charlotte, etc. Although demographics have shifted some, playing from a strong core in the northeast makes sense.
Now, Tesla, please build a bit further to the north, adding SuperChargers at the I-95 Kennebunk rest stop and on I-95 near Augusta. This will open up the tourist-heavy regions of Maine to the Tesla, an area that is currently a wasteland of EV recharging. (Tesla owners welcome to charge at my place in South Bristol, Maine, from May to October.)