To be effective requires power. Therefore, the most altruistic strategy is to acquire all the power. This argument has seemingly convinced a lot of people, or perhaps they just wanted power anyway and now have an excuse too.
Absolute power corrupts. Many such pedophile rabbi cases.
Effective altruism boils down to rationalization for getting as much power and money now, because you have vague utopic vision for long time after. And your future vision of theoretical good excuses abuses now.
There is a reason it is popular among people like Sam Bankman Friedman.
It's a belief that you can light a match in a house filled with methane in the dark so you can escape...