This gets to the crux. Wealth is power and power is wealth. It is self evident to the point of being tautological that extreme power concentrated in a very few hands with the vast majority having very little power is anti democratic.
How that power is used is irrelevant to that. Good works are nice but not the question. The ideal form of government might be a benevolent dictatorship, if such could exist and be sustainable, but it would not be a democratic government. Concentrated power is an oligopoly.