It's overpayment yes, but it's only for one year. And the first and a 3rd is not really an issue considering they should be a playoff team. The only downside here is that they now don't have the capspace or their 1st to make a deadline move. Technically this is their rental, but one could argue they will have an issue with their defense, not offense and thus this move is not the best for a contending team. On the other hand, there's tremendous upside, Kotkaniemi still has the potential to become a really good #2C.
It's gamble, but a gamble that has very high upside and very little risk.