A more fair comparison would be: Bascom AVR vs Arduino IDE
Except that people don't usually SAY "Arduino IDE." And since Arduino is a well-chosen (by chance?) name for WWW use, hardly anyone ever needs to type "Arduino IDE" in a search engine to differentiate it.
I think that when you can drastically change the google trends results by going from "Arduino" to "Arduino IDE" to "Arduino compiler" (or "Bascom IDE"), then you have a topic that google trends is not very good for evaluating. (this applies to the Bascom side as well. "Bascom AVR compiler" has practically NO usage...)