I think the issue is that someone working in public office had influence to affect that probability, and their relatives stood to gain from it.

I don’t know enough about the ethics laws to know if it was strictly illegal, but it does create a smell.

Suppose a county engineer has influence on whether oil drilling will be allowed (they don’t make policy but consult those who do), and prior to approval their relatives buy up a lot of land in the area. That engineer may not have been the deciding factor, but it seems like it runs afoul of ethics laws/standards.