Here's a quick translation of the reason for giving him this title:
The naming of Corea as doctor honoris causa shows what NTNU stands for internationally; a pluralistic creative university where Humanities and the Arts have a natural place. Trondheim Jazzorkester's cooperation with Corea has become important for the recognition and development of the jazz community at NTNU
The question you should ask yourself is: Why would a technical university honor a well-known Scientologist? Well, the story is that NTNU is a result of merging several independent colleges into one big university in the late 90s. So the people responsible for achieving this facepalmable damage to NTNUs reputation is probably from the Department of Music at NTNU.
Giving honorary degrees to renowned people isn't bad in itself, but you have to think about who you represent and what they represent before doing something like this. What if the Nobel prize for literature had been given to famous Norwegian author Knut Hamsun in 1950 instead of in 1920? That would have been unthinkable at the time due to his nazi connections and fervent support of Adolf Hitler before and under the invasion of Norway during WWII. Of course this isn't quite in the same league, but it's the principle that counts. You cannot be a university focusing on technology and science and give out honorary degrees to anti-scientific people at the same time.
PS: Sorry if the text is a bit unpolished, but this is my lunch break. I haven't seen any news articles outside Norway for this story yet, so I decided to write about it myself.