In retrospect, and knowing what we now know, that wasn't really that big of an upset. The Baltimore Orioles were, by far, the best offensive team in the American League, and a good pitching team (ERA was fourth that year). The Dodgers had great pitching but could not hit, finishing eighth in runs in a ten-team league. The Pirates may have been a much better matchup for the O's that year, or, rather, a more competitive matchup.
Those Dodgers were tailor-made for the Orioles.