Evidence has been building for some time that the Ediacaran period was more important than first realized. It looks like many lineages had already formed prior to the Cambrian. If anything, it's furthers the mystery of how all the diverse lineages could have just sprung up in such a short period of time and why is there a dearth of fossils. My own thought is that there is a discontinuity in the fossil record. As to why the fossil record is blank for this period of time, it's hard to say.