Unfortunately there is a lot of misinformation out there on this subject. Grounding actually has very little effect on how surge suppressors work. Lightning arrestors are a little different, and grounding is an issue with them.

There is no way to send the excess energy to ground. Just doesn't, and can't happen that way. Whatever energy needs to be dealt with is absorbed inside the surge suppressor. If it can take it, it works. If there is more energy than it can handle, it destroys itself trying.

The fact that the excess energy is not diverted to ground, as many people think, does not mean you do not need to consider a surge that may occur on your electrical line referenced to ground, but even then, the energy is absorbed inside the surge suppressor, even though the electrical path is to ground.

As someone mentioned, cheap surge strips often have multiple elements in parallel because MOVs have a definite shelf life and eventually will fail. If you put multiple MOVs in the surge strip, it will last longer because they won't all fail at once.