65 leaves a lot of life for a guy with the money to get the best health care.
He is the single largest owner of farmland in the US. There are many ways to profit from this, with some options being to rent it or sell it.
I don't really know why billionaires do what they do, but he is investing in all that land for some reason.
If I was one of the richest man on the planet, I would also invest in various fields, which would probably mean I end up one of the single largest owners in that field (through sheer fact I am one of the richest people on the planet).
In general I have a lot of issues with the way the worlds richest people wield power over society through ownership of everything we depend upon.