Judging by my reconstruction of the 'accident', I'd say it is the bus driver's fault.
I don't know FL laws, but the bus should allow all through traffic to pass before proceeding.
Yes, the drivers that 'blocked' the cyclist from view did stop, I suppose to be nice to the bus driver and the children on board, but by default it is the bus driver's fault.

The 'intersection' is not controlled by stop signs or lights, meaning the cyclist isn't expected to stop/slow and make sure it is clear before crossing the intersection.

Could this have been avoided? Sure. Cyclist could have slowed to see if he'd get T-boned. Cyclists shouldn't be always expected to slow at each and every intersection to see if they are going to be ran over when they have the right of way. I don't think a bus would be able to do much in the situation, considering the mass involved.