Dicerna Pharmaceuticals interview questions

The interview was easy and straightforward. Four phone call screens from HR and 3 senior scientists. Then, final virtual interview from 9 am to 4 pm with probably 15-20 people. And after all that they do not have any feedback. Just told me that they already had an internal candidate. So, why subject or even interview external candidate through so many interviews if you can not even tell why internal candidate was a better fit. I would expect a little bit feedback after being subjected to that many interviews.