Repairing broken power steering pump mounts

It's because the screws are loose, the 2 of the low and the rear one. You only see the two on the top and they look ok, then the mount cracks apart.

Try welding and using a screw lock like Loctite in the 5 screws.

Is that a timing chain cover that it bolts to? If so, first choice would be to replace the broken parts. 2nd choice, if its aluminum, get it super clean and weld it.

The problem you having addressed is that fact that it broke in the first place. It means it was over stressed and probably stressed in a way the factory never intended. I would lean toward it not being installed correctly (or even simply not being tensioned correctly). Use a torque wrench in the future.