I'm sorry but I don't see how this relates to what I said? I know Aquaman stole from Namor, I'm not denying that at all. We seem to be on the same page as my point was pretty much the same thing you said here:
Aquaman had his own cartoon in the 60's, was in the main cast of Super Friends, and is a mainstay in the iconic Justice League roster. All these things made him a household name in pop culture, while Namor remained a niche character known mostly amongst comic fans. This was the case decades before Aquaman got his own movie.