Why did Ty Cobb bat 3rd?

[steve B]

You'd have to look at the entire lineup too, to see what they expected for the whole game. Cobb batting third probably gets him just as many plate appearances as him hitting first, plus with a high average and power that maximizes whatever the guys ahead of him produce instead of wasting it by following them with another .250 hitter.
If they expected fewer runs per game, that means fewer chances for everyone, so they might have figured on maybe getting to the 5 batter in a good inning, which if the rest of the lineup is iffy, puts them pretty much restarting for the third, or having Cobb batting fourth in the third. After that it gets complicated, but being third might mean 4-5 chances at being up with men on base instead of 4-5 without people on base, or only three if he bats later.