Well, it kinda is a conspiracy and not a theory anymore. Most big cities at least in Western Europe have been trying to get rid of cars. It's part of the green/left-wing utopia mindset.

Around here they're trying to make driving so unattractive that people stop doing it "voluntarily", e.g. lower than normal speed limit city-wide, speed traps every couple hundred meters, close existing roads to traffic, reduce the number of lanes, limit which cars are allowed into the city based on arbitrary pollution labels, etc.

To be fair they actually reduced the cost of public transportation which kind of shocked me.