Most of the Hindus that come to US are usually highly educated people and come looking for work or even higher education. That takes care of first generation Hindus in US.
Coming to second generation Hindus, they grew up in Indian families where education is the most important thing. If you look at "spelling bee" on ESPN or "geography bee", more than 50% of them are Indians, so you can expect them to do "well" financially in the current scenario.
There are not many third or fourth generation Hindus in US. But, they will slowly come closer to US average once Hindu families start adopting more "American" norms of importance of education and freedom to children.
The path that Hindus (most of the Indians coming to US are Hindus) take is long (at least 7000 miles long) and hard (usually through specialized skills work visas requiring at least a bachelors degree), so you find them in good financial standing compared to other ethnicities who emigrate. So, you only see a small sample space on Indian people who meet all the above criteria. I am sure, if US were closer to India, you would see all kinds of Hindus, rich and poor in US.