Looks like they happen on average every few thousand years. We really should be looking at how we recover from such an event, and whether we can do things in the design of power grids to minimize damage.
If there were humans living on the Moon or Mars these seem like they could be even more fatal unless they were living underground.
Given how profoundly useful and powerful electronics are, perhaps events like this are why electricity and electronics are not used at large scale by organic life. Have you ever wondered why humans and other life forms are so unaffected by EM that we can subject ourselves to things like MRI scans without even noticeable effects? Maybe there has been selection against anything that is vulnerable to EM because every few thousand years anything else is culled.