Calling it a “1 hour flight” is a bit misleading when comparing transport options. The relevant number is door-to-door travel time.

Once you include getting out of Stockholm to the airport, security, boarding, the flight itself, possible baggage collection, and the trip into Umeå, I would be surprised if the total were much below 4 hours. Comparable German domestic flights such as Hamburg–Munich usually took me around 4–4.5 hours in practice in the past when traveling for work before the pandemic.

That makes the train a 6–8 hour alternative to a roughly 4-hour flight journey. Whether that is viable depends on the traveller, but it is certainly more competitive than “1 hour versus 8 hours” suggests.

I admit that for me, living about an hour north of the Hamburg main station but only 15 minutes from the airport, the plance for a business trip in Munich can still be a viable (albeit seldom taken) option. More often than not, if time permits, I take the train, work on the train. But as said - there still are situations, that make flying such a distance viable (to me).

I just wanted to point out, that it is not as clear cut as 1 hour vs. 6 to 8 hours.