Portugal? Corticeira Amorim is the exception, not the rule.
I don't mean the major buyer/exporter, I mean the many smaller families/businesses which most likely get their cork bought by Amorim - still, they get a large share of their wealth from inherited terrains.
Also, where you have oaks you can have cows or sheep. They have ways to make the most out of the land that just felt into their hands.
In Europe there's a lot of old money, or sources of income that only later generations can rip the benefits of their ancestors.
The most common example in my country is people that sustain a lot of their wealth with cork. The thing with cork is that it takes decades to build up, and a large area.
Basically people are living from their great+ grand parents buying small patches of land over many years, that had the trees already planted (or that just grew in the meanwhile).
And I'm pretty sure this reality is probably also common across the Mediterranean region.