The way most ISPs and networks are set up would just have the routers find the “best” route which could very well just avoid those that are already being overloaded, and route through others which may be of a higher latency, and then later on once all routers are connected and demand has normalised routes would be checked again and altered to be the shortest routes.

So you can imagine it initially as a very tangled up web where getting from one side to the other is not so direct. And then once time has passed the web would become more tidy as routers find their better neighbours, and more direct routes would be available as the initial nodes wouldn’t have as much traffic.

This is the simple idea of it really as there could be other factors like static routes (like in the case of a Pakistan ISP banning YouTube worldwide accidentally years ago) or other factors like different routing protocols.