He doesn't "have the authority to dictate" but he does "have an extremely influential position and his opinion is potentially very important to the non profit".

The Levine newsletter explains this very explicitly.

They have no authority on paper. They have plenty of authority in practice by virtue of exercising their power/leverage inherent in OpenAI’s dependence on them for compute resources.

The non-profit part won't ever work without Microsoft's finance/infrastructure. Satya might not have nominal power on the board, but he definitely has a power to make OpenAI miserable and proved it over the weekend.