Oh, Aquaman's been the butt of jokes in the DC universe since... well since the decades when that was how he looked. There's been repeated efforts in more recent years to make him more of a badass than just being some goober who "talks to fish".
So basically, the younger generation knows Aquaman as the kind of hero who deserves his own movie, ergo, they tried him out in the JL movie to see how fans reacted to the DCU version, and they love him enough to make having his own solo film very profitable... so they made one.
So basically, the younger generation knows Aquaman as the kind of hero who deserves his own movie, ergo, they tried him out in the JL movie to see how fans reacted to the DCU version, and they love him enough to make having his own solo film very profitable... so they made one.