(Once again, I take too long to follow through on these things. Please see Part 1 and Part 2.)
Someone with more knowledge than your humble blogger once offered the theory that the changes in the Doctor Fate strip could be attributed to a new editor wanting to switch things up. This works pretty well when the shift from Whitney Ellsworth to Mort Weisinger (even though Ellsworth was still the "official" editor) signaled a new direction for the feature almost immediately. However, the arrival of Jack Schiff to replace a drafted Weisinger doesn't quite coincide with the next radical alteration in tone. It appears to have been in the works and Schiff just went along with it.
So what exactly was this "new" Doctor Fate being introduced in More Fun Comics #85 supposed to entail? Well, believe it or not, the hook was that he had been studying medicine in his spare time and was going to become a real (medical) doctor! Inza is delighted by this and puts forth the idea that she might become a nurse. Thus, in the span of one page, Kent Nelson goes from playboy to doctor, with barely any lip service given at all to medical school. Oh, and he also drops the cape from his heroic identity.
It's a BIZARRE change that appears designed primarily to give a little direction to a strip that had lost its way in the transition to traditional superhero feature. Certainly, the next few installments focus heavily on this new setting. It just seems like an unusual concession to literalism to make Doctor Fate into a medical doctor. Certainly, Dr. Mid-Nite in All-American Comics had those bases covered.
To make matters even more confusing, over in All-Star Comics on the All-American side, this new change in Doctor Fate was never reflected in the JSA. Fate still hung onto his cape and the business of being a doctor was never even alluded to as near as I can remember. What makes this even crazier is that Gardner Fox wrote both!
Be that as it may, Doctor Fate made the leap into superhero medical drama over the course of the next few issues. He went to work at the Weatherby Free Clinic and even gained a new supporting cast member in Dr. Roland. There were also prominent speaking roles given to a nurse (or nurses) that went unidentified. I suspect this might have been meant to be Inza, but it looks like they changed their minds about that detail. Inza did stick around, though she never became a nurse.
Then things get strange and sort of hard to explain. More Fun #89 has a story that had absolutely nothing to do with the doctor thing and never depicts Kent Nelson as a doctor. Old script pulled out of mothballs? Could be, especially since #90 has another medically-themed story. But then, in #91, we see the return of Mr. Who!
To backtrack, Mr. Who was last seen in #79. Another sequel was teased, but unlike the quick follow-ups in the early months of the half-helmet Fate, it didn't come. That is, not until a year later. #92 saw a return bout with the Clock, a minor villain who had previously appeared in #81. What was going on?
It looks for all the world that Schiff, Fox, and company had abandoned any notion of Dr. Fate being more than a page-filler by this point. The medical angle was dropped, and though some mention was made of it here and there, it never figured into a plot again. Kent Nelson was only sparingly shown as a doctor. Inza finally disappeared entirely, with #90 being her last appearance in More Fun. The page count shrank. Doctor Fate had finally fallen from being a cover feature to just being something to round out the book.
There is speculation that some of the last few Fate stories were not written by Gardner Fox, though he believed he wrote the whole run of the character. Given the tone shifts, it's not hard to imagine another hand somewhere in there. There's also the fact that an unidentified wizard is claimed to be the one who gave Fate his powers, rather than Nabu. Nevertheless, it's accepted that Howard Sherman DID finally depart, and he was replaced by Jon Chester Kozlak for the last few stories.
The handwriting was on the wall for Doctor Fate. When More Fun Comics shrank to 52 pages, was anyone truly surprised that it was Fate that was given his walking papers? More Fun Comics #98 (July-August 1944) was the character's last appearance until Justice League of America #21 (August 1963). He had lost what made him unique and just sort of puttered along until getting squeezed out. It would take the Silver and Bronze Ages to restore what made Doctor Fate a cool character.