Why do traffic reduction schemes attract so many conspiracy theories?

Because automobile manufacturers and oil industry are threatened by it. In the USA we've spent the last 65 years having cars marketed to us as lifestyles. Cars are now the primary status symbol and performative affiliation signal.

The one consistent theme is against democratic governance.

Climate change, pollution are just two special cases of that.

But convincing people that democratic governance is the problem, is the deeper aim.

Anytime a government restricts free travel within its borders, it can be seen as overreach or a mechanism to control you.

My personal thoughts: if a society as a whole wants it, they will self regulate. If the society as a whole doesn’t, it’s forced.

Self regulate how? Short of lying in the roads, the self entitled (see article) will continue as before. This is why we have government.