So I've been doing a bit of research lately into the making of Nausicaä of the Valley of the Wind, yet every time I get to the part where we transition from the manga to the film, the information get sketchy. They usual information presented in wiki entries is this:
"Hideo Ogata and Yasuyoshi Tokuma, the founders of Animage and Tokuma Shoten respectively, encouraged Miyazaki to work on a film adaptation. Miyazaki initially refused, but agreed on the condition that he could direct."
Although it can be noted that Ogata, and possibly Tokuma, did advocate for Miyazaki to pursue a film adaptation, there is no account that is cited in any wiki source that validates that he initially refused but agreed on the condition he could direct. There is only one source online that has been cited for this, and it was by Dr. Marc Hairston who had a anime themed class at The University of Texas at Dallas. Interview by a G.B. Hiranuma.
So one of the conditions he placed on Animage was that he would do the manga only if they agreed that it wouldn't be made into an anime later on. They said, "yes," but within a few issues it was clear Nausicaa was very popular with the readers. So the publishers of Animage came to him and said "this is very popular, will you reconsider and let us make a movie out of this?" Originally he said, "No" but then he changed his mind and said "Ok, I'll let you do it if you let me be the director." - Dr. Marc Hairston, professor at The University of Texas at Dallas
The issue here is that Dr. Hairston never gave a source for that information. We have no idea where exactly he got that information. In the Art of Nausciaä book from April of 2019, it was noted that the process of getting the Miyazaki to work on an animated adaptation was tedious, but it was never mentioned that he flat out refused. It is noted that in multiple sources that he wanted to make the work so it couldn't be adapted to animation, but never flat out refused to make it an animated movie when approached.
Though there may be a source, such as either Suzuki or Miyazaki, that can confirm whether or not it is true that Miyazaki refused but then agreed with the condition. It would be even better if Dr. Hairston could offer up his source if he is still around or someone close who can provide the info so we can validate the wiki link on the film page. I think it's important that the information on these wiki pages be as correct as possible and that piece seems to be a glaring one.
So if you're feeling eager to find the truth about whether this was true, I would encourage everyone to dig deep. Open up your books, make a few emails/calls, and lets see if we can get to the bottom of this.