is $36 billion really that much compared to the size of the world's financial markets

The whole market, not much, so if a fund of that size wants to shift its asset class allocaton and, say, sell a few billions of bonds and buy a variety of global equity instead, it can do this. But if, instead, it wants to buy a particular security, it can't buy much relative to its own size. Liquidity constraints are very real at this size.

$1m profit is less than 1/3 of a basis point of return for a $36B fund. It's just not worth the bother, especially given how insider trading is illegal in the US.