That's one reason.Globalization
Another reason is starting with Reagan Republicans started turning a blind eye to illegal employers. This has taken money from the middle class. It has also made the rich richer. Hence the gap between rich and poor widening.
Also unions no longer exist. So labor no longer has a seat at the table. The other day I showed that since 1978 CEO pay went up 1322% and our pay only went up 18%.
So it's not just globalization.