The three major stock indexes were down less than half a percentage point at mid-morning Monday after the U.S. attacks on Iran over the weekend. Here are some likely reasons the drop hasn’t been worse: While oil prices surged, with Brent crude up more than 7% to $78 a barrel and West Texas Intermediate up more than 5% to $70 a barrel, both remained below their three-year highs of $94 and $88, respectively.