Speculation is not encouraged. And shame on you for thinking someone was just pulling a lever for fun.

Usually the hydraulic fluid gets transferred from one system to the other due to the improper setting of the parking brake over a long period of time. After takeoff, the gear uses quite a bit of fluid causing one hydraulic system to get into the yellow, while the other is completely full. the 135, 140, and 145's can transfer hydraulic fluid by pushing the toe brakes and setting the parking brake and releasing if you want to do this move about 100 times to transfer the fluid back where it came from and even the fluid quantities between both systems. Though its not a good practice, Ive seen it done many times in flight, and unfortunately crews have locked up the brakes or forgot to release the parking brake before landing.

Im not saying this is what happened, but I wanted to speak up since some idiot who posted before this hinted that a crew member might have been playing with levers for no reason.

Have a nice day.