"And if it is also on YouTube why should these people change to DTube ? They need new attractive content which is not on YouTube but only on DTube."

Again, I worked with these people... And why should anyone switch from youtube to dtube when there are no documentaries or old films there? And much less original content?
No, this will not work. Dtube has to offer as much as youtube and then more. An average youtuber spends most of youtube time watching documentaries, listening to music or maybe discovering old, curious films and series. 20-30 percent of time is spent on original content. To be blunt, the mass of youtube viewers will not switch to dtube unless it offers nice WWII documentaries to fall asleep to.
But again, that's for Dtube owners and creators to decide, what their strategy is. But if they offer only strictly original content that is exclusive to dtube... it will not work. We might wish it will, but it won't.