MoveOn claimed 3.2 million members, and gave the vote results as 197,444 for Obama and 83,084 for Clinton. Running the percentages, I found that 6.2% of MoveOn members voted for Obama, which I personally would not consider a landslide. 91.2% of MoveOn's members were not counted at all in considering the endorsement.
MoveOn claims to be a citizen organization which does what its membership wants. However, this kind of phony poll is typical of the organization. They appear to operate by deciding at the top what to do, and then devising some way of making it appear that this is a membership decision.
Why would an organization which claims to be anti-war only offer its members the options of supporting one of two candidates who both a) have voted for funding for the Iraq War, b) have refused to commit to removing all U.S. troops from Iraq during their Presidency if elected, c) favor increasing the size of the bloated military budget, and d) favor increasing the number of active duty soldiers? Before giving some ideas on the answer, let me note that this is not the first time MoveOn has disappointed its anti-war members. Just last year, MoveOn engaged in a major campaign for funding for the Iraq War.
What is MoveOn about? It was founded, well before the current Iraq War, by two wealthy businessman who were upset by both sides of the political spectrum - conservative Republicans and progressive Democrats. When it disappoints its progressive and peace-minded members, it is just reverting to form. Its basic purpose appears to be to protect the establishment against all threats.