Well really what caused that is the socialist/communist revolutions of the early 20th century.

Massive reforms (e.g. the new deal, introduction of Social Security, recognition of union rights, etc) were made in capitalist countries (along with massive anti-communist propaganda) in order to stop the spread of revolution. These were TEMPORARY concessions that we have seen wither away slowly since then. A little cut here, a program cut there, union rights weakened a bit with this law or that.

Now we're here.

Capitalism with the unionization rate of that time would be much better than what we have today.

True. And the taxes: Eisenhower individual income above $200,000 was taxed at 90%, above $300,000 at 91%, and above $400,000 at 92%. That'd trim Musk Bezos etc. down to size, fund education, fund social security etc.

Corporate taxes topped out at 52% - the tax rate was 30% for the first $25,000 in profits that a company made, and 52% for anything over that amount.

Even with inflation taken into account - $300,000 in 1950 = $3,772,843.22 in 2023........ entire generations have been robbed by the right wing.