I think this is what you meant, but it could be misread: the former is a sign, not the cause, of the latter. They’ve had aligned security policy for a long time, which is reflected in their joint decision to choose to apply to NATO.
Last year by the time Finnish leadership and people were pretty much decided on NATO, Sweden was just starting their discourse so they had to catch up not be left behind. Now somewhat ironically because of Sweden, Turkey has been delaying and objecting the membership.
Finland has also kept with updating equipment and keeping the conscription military service these past 100 years, Sweden ended their conscription and mostly been downsizing their military.
I don't think anyone thinks an attack on Gotland was ever likely, and it certainly isn't now, but if Russia's goal was to bring back all the former states of the Soviet Union, the Baltic states are on that list. And that gets pretty difficult for those two countries to stay neutral. Finland was once part of Russia too and they have a contentious history.