Keep in mind that following World War II many transit systems were worn out by heavy wartime riding caused in part by gasoline rationing. Replacing streetcars with buses was much cheaper than replacing worn out track in city streets. In addition it got rid of those "ugly" overhead wires and allowed changing streets to one-way operation to expedite motor vehicle traffic.

Also many privately owned transit companies had very poor credit because they had been operating under "service at cost" franchise agreements. Fares were set by local city councils or other government bodies. Politicians realized that if they raised transit fares, they would suffer at the next election so they kept the fares low. In some cities, Baltimore is one example, the local transit company had to keep some streetcars running because it could not buy or lease buses to replace them.

Eventually government bodies had to take over privately owned transit companies in order to provide a needed public service. Today farebox revenue rarely covers over 50% of the cost of providing service. That's why very few privately owned transit companies exist today in the United States. Tax dollars subsidize the publicly owned service.