Since it's privately held and therefore not subject to the disclosure requirements that public companies must abide by the only facts one can get are going to come from a) official company press releases, and b) leaks. With only 65 employees, any employee who came onto this site and leaked facts would be taking a huge professional risk. Barring the existence of an employee who was either incredibly naive or who wanted to commit professional suicide your original question was destined to be answered by best guesses.

As for reasons founders leave startups and the timing of their departure, you are right: there are many reasons. But usually when founders leave early in a company's startup trajectory, especially in the absence of an announced acquisition by a VC or corporation, it's a signal of issues between the Board and the founders. Eventually this will all play out and we will know more. In the mean time we just have to wait.