@rholb depends on the group, there are many causes at play.
Black communities for example are generally suffering from recent racism that explicitly kept them poor for a long time. Even once the bulk of the racist policies were gone it takes a long time for a community to recover from that. Bad habbits of poor parents (not their fault but there all the same) continue to get passed down over time and takes time to break, not to mention that racism isnt completely out of the equation either.
In other cases where there isnt a systemic cause such as with some minority communities it is just a matter of the fact that some people are going to be better performers than other through a combination of genetic abilities but also, and more importantly, bad habits being passed down, just as people who perform well have the privilege of being raised with good habits to perpetuate that.
No because you are operating under the assumption that wealth is like a pie, with a fixed amount and if one person has more than another has less.
Thats not how wealth works. Wealth is constantly being generated and destroyed in huge portions. One person can generate more wealth for themselves without, necessarily, taking it from anyone else.