I am by no means an expert when it comes to earth quakes but my hunch is that a series of smaller quakes, as in this case as the subduction takes place at the Cascadia fault line is more desirable; relieving the pressure gradually, than a single big move which could trigger a huge tsunami.
Problem is, these quakes (now over 68 in just 2 days, most of them over Mag 4) are on the side of the fault. The worst occur on the “front edge” of the moving tectonic plates, which are “fixed” very deep underground, but are now easier and able to move because the sides of the plates are loosened.