Money is not sufficient for happiness. Money is necessary to avoid certain forms of unhappiness.
It’s really not that complicated. It only appears complicated to those who: A) have enough money; and B) don’t have enough happiness.
The word they don’t understand there is “enough.” This is not entirely their fault, because much of our culture is based on preventing any of us from understanding that word. But it’s a really important word — particularly when the subject is happiness.