Part of their enormous wealth gain is due to the Tax Cuts and Jobs Act of 2017 where the rich "got a big fat raise." The rich now pay a lower tax rate than the working class — not a lower amount, but a lower percentage of their income. They have the lowest tax rate of any class in America, which is one reason we have such huge deficits.
The most discouraging and depressing aspect of all this is the fact that a lot of people — including a lot of people in this forum — support the huge disparities in wealth and massive giveaways to the wealthy. Just look at the threads about thieves pilfering railroad cars. People are outraged over the "lazy bums" stealing packages from trains. Many of the thieves are no doubt just trying to get a few bucks so they can get something to eat or buy clothing. But those outraged over the train thefts don't seem to have a problem with the wealthy pilfering billions from our economy.
We have some serious structural problems with our economy and the whole thing is going to come tumbling down if we don't do something soon.