The problem is that socialism sounds great to the unthinking. Envy is a powerful human emotion, and what sounds better than taking money away from the rich and distributing it to the have not’s.
The fallacy lies in the fact that “money/wealth” is NOT a static fixed pot which is stable and permanent. Wealth must be created continuously to be available for sharing. Only real wealth creators are mining, agriculture, manufacturing and applied product development. And almost all engaged in those activities can be classified as rich. You discourage those wealth creators, and the pot available to share shrinks.