There are multiple different logic how new windows are placed and the existing one re-ordered (or not re-ordered). Some have a logic that make look it random, if you don't know whats going on. Sometimes these behavior can be configured, or even choose from many "layouts" (these behavior and logic are often called layouts) that suits your needs. I actually use different layouts and switch between them depending on what I need. Below is a bit description of different ways how these layouts could function:

A predictable layout is the one that cuts the view in half, uses the first window opened up on the left, and then just tiles the right side, while adding new windows on the right bottom side only. This can be configured in a way that every new open window will replace the right big view, and push all other window one below to the left bottom stack in example. Another predictable one is that it cuts the view in 4 parts, left-top to right-bottom. And if all are filled and you open more windows, then the others are cut in half again when needed. Or if you want, use a spiral, that looks random at first and in my opinion was never useful anyway. And there are more ways how a layout logic could function. Not knowing how looks sometimes random.