Strontium is more common than sulfur?
The primary reason for this and other seemingly implausible features of element distribution is this: some elements are concentrated, and some are scattered. Strontium is much like calcium (which is way more abundant) and can hide as a tiny admixture in its minerals, while sulfur is pretty much on its own.

Just think of the rare earth elements. Their name is in fact a misnomer; they are not rare at all, just very scattered and thus difficult to come by, hence the relatively late discovery. On the other hand, silver and gold, which are thousands times less abundant, were known since antiquity (or probably before that).

Also, you see yourself that there are several columns with the same name "Abundance in crust", and the data for the same element vary quite significantly between the columns. This is due to the fact that finding an element's content in the crust is not easy at all. Wait, don't they say explicitly that the numbers are but estimates?