Look for the Lithuanian PM's name, Google for that - Ingrida Šimonytė declaration taiwan and Taiwan and you find.
The Lithuanian coalition agreement, signed by leaders of the Homeland Union, Liberal Movement and Freedom parties, which together won 74 seats in the 141-seat parliament on Oct. 25, binds the new government to carry out a “values-based foreign policy”.
“We will actively oppose any violation of human rights and democratic freedoms, and will defend those fighting for freedom around the world, from Belarus to Taiwan,” they said.
I suppose Lithuania's historical fondness for all things Communist may have something to do with it. That, and they are not obviously all that exposed to China's displeasure, so... why not?
I think what is happening, compared to "the dozens of other countries" before, is that a number of countries are getting fed up with Xi's China and acting in ways that they would not have 10 years ago.
It's really rather tragic - in the past most countries, maybe aside from the US, could see China taking its rightful (by size and economic weight) place in the sun and would have seen no reason to oppose it in the same way as they did the USSR. On the other hand, China's CCP thrives on nationalism, and internal and external coercion, so is over-reaching too early.
It didn't have to be Cold War 2. China isn't really Communist anymore in nature and isn't inherently an internationalist nuisance, "just" a dictatorship. Looks like relations are heading that way however.
Edit: re "the rambling".
First the question asks why Lithuania is departing from hitherto common practice (see also Fizz's answer for internal political reasons). Second, while that's my take on it, I didn't invent it:
China’s ‘wolf warrior’ diplomacy is anything but effective
Chinese foreign policy has become more assertive and heavy-handed in the last decade, and as a result it has alienated some of its neighbors and fueled greater wariness of Beijing’s intentions in the region. As China has become wealthier and more powerful, the Chinese government has shown greater willingness to throw its weight around even at the cost of antagonizing and insulting other governments.
China Has an Image Problem—but Knows How to Fix It
It isn’t just the United States. Around the world, unfavorable views of China have reached unprecedented heights in the last year, with the percentage of individuals having in Chinese leadership to “do the right thing” in world affairs rising by more than 15 percent across countries like Australia, Germany, Italy, the Netherlands, and the United Kingdom. The reaction among the Italian public is particularly noteworthy, given the China has offered the country during the COVID-19 pandemic.
Too soon, too loud: Chinese foreign policy advisers tell ‘Wolf Warrior’ diplomats to tone it down
The speech by Shi, who has been an adviser to the State Council, China’s cabinet, since 2011, was posted on an official university social media account on Monday. He also said China should change course “as soon as possible” and instead take a more nuanced approach to the rising anti-China sentiment among policymakers in Washington.
“When both the official and non-official media are all adopting an aggressive tone when reporting about the US, it’s not conducive to [turning] public opinion,” he said, suggesting Beijing should direct some of its official media to take a more conciliatory tone.
Shi also called for a halt to the debate about the origin of the virus “because this is only exacerbating the blame game between China and the US”, saying that it would take time to find an answer.