Come here and you can understand how they work. I have been here for 7-8 days now and I can see it easily (well, one of my scientific group leaders is Japanese and I have been working with him for 5 years already).
1. When they plan big investment then they want to control it 100%.
2. They trust Tommi and it is one of the most important thing for them. Winning their respect is not easy job and it is among the most important things here
3. Cologne is too far from here and no proper connection with their headquarter. If they take business class ticket to Finland then they can have proper good-night sleep and they are on their base in 10 hours. It is additional 4 hours to Germany (all my German and even Italian colleagues here came by Finnair via Helsinki) + drive to Cologne, that means they loose a day=big money etc. It just does not fit into their plans.
4. They did not had good memories with Cologne base = better to use it as some kind of sub-base.