Question: There is this startup founded by well known people in the industry. 
They are making a very good product and I'll be proud to work on it, but my first motivation to apply is to be with (and to learn from) these great masters.

Should I tell them or keep it for me and focus on the product and the global company feeling?

Answer: 
I am sure you can say that, but don't make it too dramatic. Include the performance of the company and mention you are excited to join such a successful company founded and run by the leaders. At the end of the day, we want to work with the best people and learn from them.
There is nothing wrong in telling them that during the interview. It will do you only good. It will show that you have a reason why you have a proper reason why you have applied to the company, and not like applying to any other company. It will show that you really have done your background research about the company. This will definitely give you an upper-hand over your competitors in the interview.