Canada

Simple why it's so effective:

Institutions are facing increasingly insurmountable problems, and people are not dealing with the consequences and stress that comes from these problems. They want answers and solutions.

Institutions ask for you to have patience and give them time to fix the issues. Problem: people already don't believe that the institutions are fixing things, so you can't rely on them to fix it. The solution, they feel, has to come from elsewhere.

Left-wing propaganda says that the institution is broken, they will fix it. They want to take the money away from the ultra rich and give it back to the public as a form of equalization. If you are part of the ultra rich, you don't like this.

Right-wing propaganda says the institution is broken, they will fix it. Right-wingers generally believe in the accumulation of capital for themselves via "merit", which means the upper class and billionaires are likely to be supporting / using them.

People believe that things need to be fixed (which is likely true). Only left-wing and right-wing propaganda say that the institution needs to be fixed, it definitely isn't coming from the institution itself.

The ultra rich fund whichever propaganda will allow them to retain their own benefits and works to suppress the propaganda of the ones who work against their interests.

Hence, right-wing propaganda is massively inflated to support fixing a system that allows retaining wealth, while they suppress left-wing propaganda which says wealth needs to be redistributed to the masses.