If by working the weekends you mean seven-day work weeks on a regular basis, I strongly believe you were doing the right thing.
The health of your employees is a much bigger priority than business or development. They're not human resources, they're people with families and loved ones and the need to have a day off. Unless you were on the verge of curing cancer, there is no reason to work people like that.
You were in a bad situation - it sounds like there were huge problems with upper management - and you did the right thing. Unfortunately doing the right thing doesn't guarantee success. No doubt you made a lot of mistakes too - I've been there and it hurts - but that doesn't sound like one of them.
To me it's a sign in your favor that the team left after you did - if you were the problem, they would have left before you did. I don't think you can expect them to be happy when they're working weekends and (what sounds like professional developers) are doing manual data entry for weeks on end.
