@bythewell - There are different things that can be done. For example, foster kids might only be placed with families who show an intention to adopt them.
Unfortunately, the reason so many foster kids end up in bad situations is that there is often no other place to put them. There are far more kids in the system than there are people who are willing to take them in, for any reason.
If more good people put themselves forward to help, there would quickly be a reduction in foster child abuse.