Politicians and NIMBYs killed mass transit in the US long before Musk entered the picture. In fact, Boring Co is a direct reaction to mass transit projects routinely being turned to boondoggles by politics, corruption, mismanagement, and obstructionism — building mass transit via the traditional means is practically impossible.
I won't pretend that the Boring Co's loops are efficient or a real solution but I don't believe that pinning the blame on it is quite right.
General Motors did, with help from others in automobile, oil, and tyre industries:
The General Motors streetcar conspiracy refers to convictions of General Motors (GM) and other companies that were involved in monopolizing the sale of buses and supplies to National City Lines (NCL) and its subsidiaries, and to allegations that the defendants conspired to own or control transit systems, in violation of Section 1 of the Sherman Antitrust Act. The suit created lingering suspicions that the defendants had in fact plotted to dismantle streetcar systems in many cities in the United States as an attempt to monopolize surface transportation.
Between 1938 and 1950, National City Lines and its subsidiaries, American City Lines and Pacific City Lines—with investment from GM, Firestone Tire, Standard Oil of California (through a subsidiary), Federal Engineering, Phillips Petroleum, and Mack Trucks—gained control of additional transit systems in about 25 cities.[3] Systems included St. Louis, Baltimore, Los Angeles, and Oakland. NCL often converted streetcars to bus operations in that period, although electric traction was preserved or expanded in some locations. Other systems, such as San Diego's, were converted by outgrowths of the City Lines. Most of the companies involved were convicted in 1949 of conspiracy to monopolize interstate commerce in the sale of buses, fuel, and supplies to NCL subsidiaries, but were acquitted of conspiring to monopolize the transit industry.
Musk is proposing to make an expensive part, boring tunnels, cheaper. But then he also proposes a fundamentally boneheaded change that makes any improved efficiency there much worse: individual vehicles which are fundamentally unscalable.
So I wish he would keep the good part, cheaper tunnels, but not sabotage those tunnels with an unworkable vehicle proposal. It also gives a ton of power to the obstructionists to sabotage real transit projects and increase their costs, because they can say "let's try what Musk is proposing".
I won't pretend that the Boring Co's loops are efficient or a real solution but I don't believe that pinning the blame on it is quite right.