I'm not sure static typing or a compiled language would have helped much. The scope of the undertaking was certainly enormous, but it was so ahead of its time in many aspects. It tried to combine an email client, calendar, scheduler, note-taking and more; any one of them would have been a serious task. Furthermore, they had to develop additional protocols and formats for reliable communications, and you may recognize them: CalDAV & CardDAV. The main software project could not withstand the changing requirements and complexity.

I have read the book, and I don't think it's a case study of Python - it's a case study on releasing an MVP. Chandler tried to do every.single.thing right out of the gate, and got bogged down. What would have happened if it just focused on email?

I still use Gnus for mailing lists and Thunderbird for all direct email. Almost 20 years ago I spent more than 2 whole days to configure every detail of Gnus to my liking and still use the same configuration mostly unchanged.

We can date ourselves by what email clients we have used!