In the case of the US, had voting been mandatory, victory of the voters courted would have been so ridiculously one sided that it would blow apart the idea that there are two actual opposing factions of equal desire of the will of the people. This has actually been acknowledged out loud by the current leader of the faction that is running the side that won.
> I thought that Trump more or less did call his voters dumb on multiple occasions
I think he has, and I know he has very famously called them blindly loyal sheep (not in those words, the exact phrase was: "I could stand in the middle of Fifth Avenue and shoot somebody, and I wouldn't lose any voters, OK?").