Why limit the comment to modern philanthropy? I doubt anyone, in meaningful numbers, has ever sought to undermine their own position in society. That would include anyone nominally seeking to “change things for the better.”
Let's assume (without loss of generality) that your $400k income is from a salaried job at some company. Suppose that there is an NGO fighting to abolish said company on moral grounds. Would you be willing to donate your money to that organization?
Which, even if that NGO succeeded, wouldn't undermine the position in society. If Facebook were dismantled, the employees just switch to Google, Amazon & Co.