I get the sense that you’ve read a lot of theory without any observational facts.
The vast majority of the 1% and 0.1% get most of their income from labor nowadays. This is a phenomenon called “The Rise of the Working Rich”. This looks like CEO compensation, top athletes, too musicians, business owners, and so on. On average, the 0.1% gets about 20% of their income from investments and 60%+ from their actual labor.
70% of the Forbes 400 are self-made, the vast majority of millionaires receive $10k or less in total inheritance, 11% of Americans will be in the 1% for at least 1 year in their lifetime, and the majority of Americans will be in the top 20% for at least 1 year in their lifetime. If you chop off the top 1% in developed countries, their Gini coefficients are very similar, implying that the US doesn’t have exceptional levels of suffering from inequality, it just produces a lot of rich people.