I'm a Lithuanian who is living in the UK. Lithuania before the Soviet annexation was a rural and backward peasant state, where there did not exist any form of a communist party, especially compared to its brothers (Latvia, Estonia). Lithuania had a parliament but it was a fascist backing, such that (as you stated) Antanas Smetona was a fascist and he openly admired Mussolini. On top of that, nazi collaboration was a thing and definitely existed in Lithuania against the Soviets (Note that the Baltic people follow the "double genocide theory" bullshit). When Lithuania was annexed, it had a communist party, while Latvia had a communist party since the Bolsheviks, making it one of the earliest communist parties. Lithuania has had a lot of reactionary uptake, including the Forest Brothers, which most of the action take place in, and has killed innocent civilians.
According to Human Rights in the Soviet Union, Lithuanian Nationalism still continued to exist even under the Khrushchev and Brezhnev era of the USSR. The dissolution started with the CIA (obviously) and it was not out of the popularity of the masses. The Lithuanian Nationalists staged a bloody provocation in order to frame a Soviet Attack.. It is clear that Lithuania had its reactionary nationalism even during the Soviet era.
Why do Lithuanians support the modern government? Because they want to. They're want to act more 'western' compared to the great 'Russian threat'. Western in the sense being distinct from Russia. I have also not been taught of Lithuanian history in the USSR and had to search these things for myself (Hence why I am posting sources). It's a shame. Lithuania could've been a great nation (in the socialist sense) however due to the revisionism of the USSR on top of the Lithuanian nationalism, I cannot call myself a Lithuanian patriot, because I would be associated with the reactionaries that kept this country running and also drowning itself of air as it sends resources to the Ukraine.