It's obviously that the DRS-BSL link doesn't fit to their strategy.
I wouldn't say so. Obviously easyJet registered many Passengers from the Dresden region on the SXF-BSL flights.
Also, don't forget that in the last few years thousands of Germans immigrated to Switzerland, many of them from the former Eastern part of the country. These immigrants are usually well educated with a not so bad salary.
Keep in mind that Basel airport is only a few miles away from the German border, so the new flights also serve "domestic" South Germany-Dresden passengers.