I got to the part of "It wasn't giving me joy anymore" and, well... that accounts for a large portion of why anybody is no longer [fill_in_blank]. I believe circumstances make up most of the rest.
The first part of what you say is true, but that can result from systemic deficiencies or incompatibilities, which was the case here.
Education is notorious for having people quit due to feeling disillusioned, constrained, or opposed by the systems around it. The National Association of Schoolmasters Union of Women Teachers in the UK did a survey of its members in 2013 and found 84% felt demoralized with 50% having considered quitting the profession entirely in the past 12 months.
I read it as "It wasn't giving me joy anymore and I had plenty of financially viable options that were probably the result of leveraging my academic title."
