Bitcoin is decentralized, but is the internet?

I was thinking.. Bitcoins decentralization is based on nodes and nodes are pretty lightweight, they can run on old computers and raspberry pi’s. Why can’t someone make thousands of nodes? - because every node needs an ip address, and ip addresses are issued by regulated entitys / ISP’s. Can an ISP or government not just make so many nodes that it can do a 51% attack.

I know that if this really was the case it already happend, so what proves this wrong?