This world is spinning, what is below can become above, and what is above can become below. Likewise, a person's economic situation can definitely change. A big example is people who are very rich but become poor and this often happens. Because that's what the wheel of life is like. However, for people who were originally rich and whose fate changed to become poor, this does not mean that it just happened. But most likely, it was the result of his own actions. Such as not being able to manage money well, having fun with the lifestyle, and also not thinking long about the future. So because of his actions, his fate changed.
You are completely right. And this situation has been visible along generations during the whole story of the world. A rich family today isn't assured to remain rich if their heirs didn't develop a mindset of responsability, financial management, long term business vision and cost containment during crisis times (even the riches have to know when to reduce expenses).
Sometimes the householder is so concerned about running his businesses that he forgets or neglects the fact he should take some time to teach his children to maintain his legacy once he is gone. Then he has those children living alienated only spending and wasting money without thinking on what tomorrow will bring.
Once the guys like joe Biden will go away their kids can't handle nothing maximum will be that they easy targets for foreign sharp minded people to take advanched of the situation.
There are many native sharp minded americans as well, ready and willing to thrive in life. People who are working hard and looking for an opportunity, just like the foreigners who came to USA with that purpose in mind. Families rising and falling financially doesn't mean the country is going to be ran by foreigners.