The iphone pro has also plateaued. High end phones are a niche and not a very big niche globally. When you consider the TAM for $2k non-Apple phones, folding ones do have a massive share.popularity implies growth, folds market has already plateaued.
there is no visible proof of the popularity that you alleged, let alone ‘massive’
Your bias is showing, and I’m betting when apple tell you your bias has changed you’ll be saying how great folding iphones are.