From that article: "Its videos now collectively garner some 5.5 billion views every month, according to the source."
Youtube view CPM's can range from $.70 to $7 and for these multichannel networks, who are able to contact advertisers directly, the CPM's can be much higher. For maker studios, who take a cut from those CPM's, that's a multi-million dollar company
I don't have any links to provide exact numbers, nor do I think producers would feel comfortable revealing them, and no there aren't any producers making billions but nevertheless, production companies like Roosterteeth, Rocketjump, Barely Digital are able to employ a large number of people and produce content exclusively for the internet. Plenty of youtube-based filmmakers make six figures a year through ad revenue and merchandise based on their productions