I've been actively producing content for under 3 years, though I've had the channel for 6. Currently, I have 137 videos, 16,805 views and 39 subscribers (I gained two very recently, which pleases me ^_^). In my case, it was taking long breaks. Unless you provide more information, it can be pretty hard to tell just based off of that.
What kind of videos is he uploading? Is he using good tags and titles? What about the description box?
What's his schedule?
Have there been any dramatic life changes or personal obstacles that kept him from uploading for long stints?
Did they engage in sub4sub and thus have dead subs who don't care to watch and share their videos?
These are things that I know have hindered my growth. I've taken two pretty long hiatuses from youtube (3 and 7 months) , which absolutely murdered my channel's capability to grow when I did return the first time (that was the longest break, I know my subs had forgotten all about me and I lost some subscribers during that break). One thing I've learned is that consistency is key, but I don't know anything about this guy's channel or content, so I can't verify that he's inconsistent, all I can say is that's what killed my growth, since I'm (numbers-wise) in a similar position as he is, not that it's a competition, just trying to help paint why his channel might not be experiencing the growth people come to expect after years (or sometimes even just months) on youtube.
One other thing that hindered my growth until recently - I wasn't utilizing social media to share my videos until perhaps a month or so after I got back from my last hiatus. Now, I'm in groups on facebook, sharing to twitter, tumblr and instagram and reddit. This person could also not be sharing their videos? Maybe they could try a channel revamp, if they haven't already. I'm always doing stuff to make my channel and videos look better, which I believe has helped - I did get good feedback once, so that was nice. I've also been treating my description box differently, after binge watching some Roberto Blake and Derral Eves videos.
Just with what we're given about the channel, all we can do is speculate as to why they aren't experiencing tremendous growth. I only posted this because since our numbers are similar, and I can speak from experience about where I've gone wrong and killed my channel. Idk if this'll help anyone, but doing a total revamp on my channel has been helping me so far - and the mindset that there's always room for improvement.
