Jim,

In short:

In the 30s, the US (as most of the countries) were an isolated country with a 'simple' economic structure. That's why the 'Great Depression' didn't spread to other countries.
In the 80s 'crisis', the impact of the oil price on the global market was much bigger than nowadays. OPEC controlled the influx into the market and all oil flowed basically to the 25 richest countries on earth.

Second issue:
Buffet still has a lot of shares and related products. If everyone keeps selling, his worth goes down and down. He doesn't need that.