Wasn't feudalism mainly a hierarchical means of controlling land and the people that worked the land? If you don't actually need peasants/serfs to do anything then you wouldn't need feudalism.
One of the drivers for feudalism was the prevalence of cavalry in warfare starting after about 700AD. Mounted knights are expensive to maintain, hence the solution of providing land grants in exchange for military service. It's a medieval version of the military-industrial complex.
The connection between mounted warfare and feudalism is controversial [1] but it's common enough that societies adopt social structures optimized for defense. There were almost certainly multiple reasons for the prevalence of feudal relations.
Not exactly. Feudalism was rent seeking from top to bottom. Local Barons obtained the right to get rent from peasants who lived on their land. In turn they paid to their local Earl who paid to the local Duke and so on up the ladder to the King. Without the peasants at the bottom their would have been no feudalism. Of note, the peasants alone were generally forbidden from bearing arms.
The connection between mounted warfare and feudalism is controversial [1] but it's common enough that societies adopt social structures optimized for defense. There were almost certainly multiple reasons for the prevalence of feudal relations.
[1] https://en.wikipedia.org/wiki/Great_Stirrup_Controversy