There was always a certain jaunti- and lightheartedness in Slade's presentation (in contrast to Jim Lea battling with his depressions, but then depressive jesters are nothing new) that didn't sit well with people who liked 'serious' heavy music. That "Hey, we're entertainers!"-approach. It had people usually underestimate their musical clout. You had to see them live to realize that they weren't just a pop hits delivering machine. And that Reading 1980 experience where they somehow end up on a festival bill in the last minute where no one expects much from them and they then steal the show wasn't a first time for them. A similar thing had happened in the early 70ies when they played on a UK festival otherwise populated by more PROG image 'serious' bands and took the largely non-teenage audience by storm, baffling everyone by how well and energetic they could play. (They had the energy of the J. Geils Band on a good night.)
But Chas Chandler wanted to see the single hits flowing for a young teenage audience rather than establish his proteges as 'serious artists'. What he forgot was that biologically speaking bands that focus only on the young teenage market generally only have a shelf life of three years or so before their audience develops either breasts or beards and moves on to other music. And those three years (where they ruled the UK charts) is basically what Slade had. It type-cast them forever and they could never really leave the image behind.
That "good fun"-aspect in their music did them no favors in America I think. And of course their vids in the rising MTV era were made on the go and failed to project anything to win an MTV audience over. For a band that had widely received acclaim for their performance in the semi-documentary Flame movie (about a fictitious up and coming band named "Flame" consisting of the four Slade members, the film was even lauded by critics who had otherwise been dismissive of Slade's musical output), Slade were really hapless/naive in creating a new video image of themselves.
And finally, I think they would have needed to be put in the hands of an experienced and professional American management organisation with some clout in the mid-80ies. But by then Noddy Holder was fed up with life on the road and didn't want to commit to extensive touring anymore. He's never returned to it and prefers being a family man and a - light-hearted - TV and radio personality.
