100% of the power over the bitcoin protocol is held by the rolling set of individuals who are receiving bitcoin in exchange for something else. A node’s power over the rules of the network is directly proportional to what goods/services (or other currencies) will be withheld from a trade if that node rejects a transaction. Miners and developers etc only have power that is given to them by that set of participants. If they ignore those participants then devs write code no one will run, and miners mine a coin that no one will buy.