The Finns have been on the fence since the Cold War began. Part of it was Finland's alliance with the Nazis and war with the Soviets during WWII. Part of it is probably the hope that they can emerge unscathed while the West wards off Russia. Now that the Russians appear to be peeling off anyone not aligned with the West via a defense treaty, they are starting make noises about joining NATO. My guess is that they'll join minutes after Russia crosses the Finnish border.
I think Finland was banned by a peace treaty from joining NATO after fighting a war with the Soviets. They would dearly have liked to have joined NATO if they could have done.
There was an unspoken agreement between Finland and Russia that said Finland stayed out of NATO, but could align towards the West.
But Russian nationalist view Finland as part of Great Russia. The Finns have fought the Russians before, and know it won’t be as easy this time.
Sadly for them, NATO isn’t going to help them. The members all depend on Russian gas to keep the lights on