It is actually kinda like this:
You start a niche tube and do unique long descriptions and unique titles.
Your site progresses daily in search engines (it is beautiful to watch it grow day by day).
At some moment in time space continuum, your tube will get the attention of site scrapers and cloners.
They'll pop 3-4-5 scrambled clones of your site and enhance it with some backlinks.
You'll continue writing your descriptions / titles / texts but you'll also notice your site is suddenly stagnating in serps.
Your site will start dropping in se traffic, because those clones will actually get more benefit from your unique texts (coz it is a game on what google indexes first).
There you go
