Wasn't Baby it's You also on Billboard? Bigger reach than Variety.
Being on Vevo's main web page helps exposure as well
Also, we saw advertisements for Baby it's You for a couple of weeks on web sites and on You tube, none of which has been done to promote "The Letter"
Part of the video/Youtube/ social media game is putting out content consistently. At best Haley's has been start and stop, so it's hard to gain subscribers.
I've been posting video on a consistent basis for five years, even more so since Haley joined PMJ, promoted my video here, on twitter and sometimes on Instagram and still can only manage, just crossed 30,000 subscribers. IF Team Haley spent more resources on that side of promotion, she'd get more views.
That's the reason I reworked some of my videos and sent them to Haley if she wanted to use them (even offered the 'raw', unedited files for her Team to edit), putting out content if good enough, giving people a reason to visit her channel, but until there's a dedication to promote and support videos of Haley, the numbers on her own channel won't grow as quickly as we might like...