You know it - "Go placidly amid the noise and the haste, and remember what peace there may be in silence. As far as possible, without surrender, be on good terms with all persons... "
This led to researching the variations of the Latin root word....Desideramus basically means, "Something we need to do" and in each case, the reason the books were written was because the author found herself saying, "Somebody needs to do something".
In the case of the Gary the Go-Cart books, she was working in Environmental Science with energy companies on their various environmental issues and was appalled by the misinformation in the news. She had seen mountains of data that supported the petroleum industry and realized it would be impossible to get people to see all that data. She felt like someone needed to make it simple enough for a kid to understand. It seemed to her that usually when she had what she thought was a great idea, someone else did too and she would see it happen. In this case, it didn't happen, so she wrote the books.
As to the Biden book, it was basically the same thing. 2020 saw massive rioting and the persecution of conservatives. Ms. Denson felt like conservatives needed more political humor. (For some reason most of the good comedians are liberals!) Then the idea for this book came to her and again she knew it was something that just had to be done.