Final answer:
Syco likely assumed One Direction's audience to be teenagers and young adults who enjoy pop music, are active on social media, and use online streaming services.
Step-by-step explanation:
The assumptions that Syco, the music label owned by Simon Cowell, has made about One Direction's audience potentially include demographic targeting, musical preferences, and consumer behavior.
Simon Cowell's label likely assumed that the band's primary audience would be teenagers and young adults who favor pop music and form part of a digital-savvy generation that follows artists through social media platforms and online streaming services.
The marketing campaigns and branding strategies would, therefore, be geared towards that section of the music-listening public, anchored on the assumption that a strong online presence and wide-reaching social media strategy could effectively promote One Direction's music and merchandise.