The trivially true answer is "by a variety of means" but obviously it's trends and patterns that are of real interest.

And this brings us close to studies of "social mobility" (glossing over the difference between class and wealth - which - taking a long perspective - can be assumed to be roughly synonymous).

And with social mobility between generations usually fairly low in general - the next most trivially true answer is "because their ancestors were".

Attempts to trace this back to some origin myth is slightly silly but on the whole your answer to the "where did it all begin" question indicates your political colour.

If you tend to answer "Because they stole it by force" then you're probably on the left. And if you tend to answer "Because they created a strong leadership that protected a group from other groups" that places you on the right.

Of course - pure examples of bandits vs noble warrior kings are rare but I suspect there's more of the former in history than the latter. ;-)

In feudalism, land is the reward you get from the Crown by being useful to the Crown. Land lets you charge rent. Rent makes you rich.