I think he thought the casualty rate would have been substantially higher.
A bad rationale—the strategy should have been adapted to mitigate that.
But I fear his leftist detractors may be right, and it may have been a matter of unfinished business for the Bush family.
Afghanistan is on 1 side of Iran, Iraq is on the other. The longer game was to neutralize Iran with a squeeze play, but the rats took the house in 2006, GWB wouldn’t defend himself from the leftist attack dogs, the electorate got swayed and the nomination of McCain made them put Obama in power, we abandoned Iraq, Obama gave the deal to Iran, and here we are.