Why would loss hydraulic power keep the gear from locking down?
It wouldn't. Locking is assisted by springs on the MLG and aerodynamic forces on the NLG.
How did they even get the main gear doors open and the nose gear unlocked with without hydraulic power (emergancy gear release)? Something does not make sense to me.
In the event of green (L) system loss, there is a hand crank located on the center pedestal to operate the gear. This event must have been a fluid leak as this aircraft has a PTU to transfer power from the yellow (R) system should the L engine pump fail.