Perhaps you need a better map. Gotland is a prime target for Russians. Establishing air defense batteries on Gotland, along with capturing the Suwalki gap between Poland and Lithuania, are two key steps of invading the Baltics. Suwalki cuts the land supply route and Gotland the air and sea routes.
To prevent liberation of Gotland and keep Swedish armed forces busy, they would then terrorize the remaining parts of Sweden with drones and missile attacks on cities the same way they do in Ukraine. Even Sweden isn't rich enough to buy enough air defense systems for that, hence the need for NATO to get access to pooled resources.
It's a simple calculus.
It's wrong. But it's certainly very simple :)
You forgot about how an invasion force is supposed to swim across the baltic.
After all, Russia can't move a huge fleet in there, because access is between sweden and denmark. So they'd have to use whatever they already have in there.
And sea invasions are more complicated than land invasions.
The only wrong thing here is the idea that the invasion of Gotland would have to look like Normandy landings.
Well well well… the request to join NATO was done just a few months BEFORE the election, after several changes of government since the previous elections.
People in power specifically didn't want the people's opinion about that one.
But just to be on the safe side, they also did a lot of mediatic fear mongering about russia invading sweden very soon™, which is ludicrous if you look at a map and see that there's a sea in between.
Anyway in sweden the ruling class had wanted to join NATO for at least 10 years, if not more. But the people would have not liked severe welfare cuts to buy expensive bombs. However the invasion of ukraine provided the perfect excuse.