It's easy to forget that things change, and change tends to be exponential. What YouTube did was remove the hassle and fiction in posting videos online. It used to take a lot of effort, and many people who didn't know enough didn't realize the complexities involved.
The author here calls youtube an ftp site, and in doing so ignores what set youtube apart. Youtube automatically transcoded videos, it played videos in your browser inline with other content, and it was free. All you had to do was make your video small enough to upload and YouTube did the rest. You didn't have to worry about codecs, or hosting, or bandwidth Nichols, or domain registration, or any of that. Previously if you wanted to host a video online you had to optimize the encoding, pay for bandwidth, and worry about compatibility depending on encoding. Then your video would be viewed by a browser plugin, usually as a bare video.
Plus there was a catch-22, if your video got too popular it would cost a ton of money to host. Youtube got rid of all that hassle, and in so doing naturally started to acquire content and users. Once the critical mass network effect kicked in then youtube became the default place to view and post any and all video content. From there it should have been obvious to anyone paying sufficient attention that the quality would only go up, the costs of bandwidth and servers would only go down and with a sufficient number of viewers that some monetization strategy or another was likely to be effective.
People made similar mistakes about tons of new technologies, the commonality is often assuming that the launch state is the end state, and not square one of a massive acceleration in sophistication, features, etc.