Wasn't Thor: Love and Thunder also postponed due to the situation surrounding COVID-19? That didn't help matters, either.
I recall reading somewhere that Natalie Portman had had it with Marvel movies, especially those involving (or not) Jane Foster. She was on the verge of walking away when this project came along, and even then it took Jane Foster becoming Thor to keep Natalie Portman attached to the project. It also helped that the comics themselves featured a storyline where Mjolnir chose her to be Thor, but each time she assumed the role as "Goddess of Thunder" her lifespan as Jane Foster was cut short by some amount.
I'm trying to recall what I had read as far back as 2019, so I may be off or way off here.
Also, wasn't Thor himself looking more like a taller version of George Coastanza than King Leonidas from 300 in between Thor movies? When did his transformation back to Avengers-vintage Thor take place?
With the turn Disney has taken in recent years, it's just as well that the last MCU movie I had seen was Ant Man and the Wasp, so I'm sure I've missed a few things over the last 3 years. I just expected much more from Thor 4,