The PVC flex tends to shrink with age, unlike most of US.
As a result, it can put quite a pull on things. Look at your pump, and see if you think that pulling actions might be the reason the motor was pulled off it's mount.
It's not tough to work with PVC flex - although I ALWAYS heat it up as I'm working with it: sometimes just setting it in the sun on a hot day is enough, other times I run hot water through it, or I may use my heat gun or even a torch. When you do the repair, be sure you use primer AND PVC cement, and allow just a bit longer pieces than you think you need to allow for future shrinking. Be aware that plumbing on the other side of the pump may have also shortened up over time, so don't worry if the mounting bolts don't line up in the exact same location when you are done. You may have to put a lag screw or bolt into a slightly offset location: it should be fine as long as the pump doesn't flop around or vibrate noisily.
I know it may look odd if you end up with the pump sitting a little bit crooked, but it will work just fine as long as you make good plumbing joints and secure the pump in it's new location.
HTH