This data is meaningless because:
1. There is no benchmark and we need one because SimilarWeb is based on a panel. The less people in that panel, the less total traffic to any website.
2. Most likely cause is more app usage and less desktop usage.
Also can we please stop using SimilarWeb as some sort of authority reference? Their panel isnt humongous. Despite the fact they pay Chrome extension owners and later hijack the code to track everyone who installs it.