But wasn't the wealth before capitalism all in the hands of feudal lords, who didn't get it by enterprise but by conquest?
No. Conquest was expensive at best paid for itself through theft or 'sacking', often that was insufficient. The peasants and artisans would produce food and goods, sell them in trade, and Feudal Lords would tax them in exchange for infrastructure investments, keeping the peace, protecting trade routes etc.
It was the people making things that created the wealth. They took raw materials (seeds and soil, metal, wood etc) and turned them into something more valuable than they were before the labour was added.
Feudal Lords added value by inhibiting banditry, raiding and thus stabilising trade etc. They did this, in part, by paying a specialist who didn't create or make anything - the soldier.
Capitalism does benefit the whole society in a way the feudal system of course did not.
Capitalism was born when people who were Feudal Lords in name, decided to start lending money and borrowing money tactically for investments (such as purchasing bulk raw materials from overseas such as silk) and ignoring usury regulations which the Christian and Muslim Feudal Lords were constraining themselves with.
Edited by Modulous, : No reason given.