How does BRK both (1) beat market returns, and (2) still trade at a low multiple?

As many of us know, BRK has beaten the S&P 500 over 1, 2, 5, 10, and 25 year (and probably more) time horizons. Just amazing consistency. What I didn't appreciate until recently is that it still trades at a P/E of 12.5. How does a company deliver a 250+% return over the last 10 years and still trade at such a rational multiple? Most companies that have delivered outsized returns do so because their "P" drastically outpaces their "E" because of investor enthusiasm or fanciful expectations about possible future revenue. Not BRK. BRK consistently delivers the actual "E" to justify their "P." For decades.

Second question. Given the above, and given its status as basically its own self-contained diversified portfolio, why not justy park everything in BRK, instead of, say, VOO?