I partially agree with your theory. Mainly that it is one guy. I base this on the internet searches done prior to the kidnapping.
Based on those searches my theory is that a person from Arizona wanted big money and planned this months before.
He found a celeb's mom living close enough in an area that he is familiar with.
He scoped the area both online and in person, i think.
Before i knew about these internet searches i really thought robbery gone wrong and Nancy is sadly no longer amongst us.
Now however, i start to believe that there is a possibility she is being kept alive in AZ en that this was a planned kidnapping for ransom.
Why else would someone so specifically websearch her house (both her adress and pictures) and the salary of SG?
This case has me going in circles continuously.
JMO
Source info on websearches:
Google searches for Nancy Guthrie's address occurred weeks before the suspected kidnapping of Savannah Guthrie's mother in Tucson, Arizona.
www.foxnews.com