The seller was worried about himself. Yeah it's a flat out dick move, but it happens.
Last year it happened to me (and others on here) with a MB in NJ.
I just got out of the bank with cash and I get an email (not even a call) that someone closer than me was on their way to look at it. I was 2 hours away. Thankfully I didn't waste gas, but I took off of work for nothing.
That cash went towards my first home purchase 2 months later so it worked out.