It's impossible to understand motivations without understanding context. Belarus' president Alexander Lukashenko has been politically isolated for a long time, and so there's only so many people he could learn from.
After the American-led invasion of Iraq in 2003 (and owing to Belarusian dealings with Iraq and Iran), the term "the last dictatorship in Europe" was used to describe Belarus. Lukashenko has been in power for over 25 years, and his rule has been characterised by prioritising stability over change (political, economic, cultural).
Lukashenko doesn't have many friends. Vladimir Putin's Russia has effectively subsidised Belarus with cheap natural gas, and Russian oil and gas exports are piped through Belarus too. Lukashenko's other friend is Turkish president Recep Tayyip Erdogan.
During the height of the migrant crisis during the worst years of the war in Syria, the EU agreed to pay Turkey to reduce the flow of people attempting to enter the EU from Turkey. Erdogan has understood the power of using refugees for bargaining with the EU, and Putin understands the power of creating trouble along borders (e.g. pro-Russian separatists in Georgia, Ukraine, Moldova are recognised and supported only by Russia).
While Belarus has endured sanctions in the past, they never posed an existential threat to Lukashenko's rule. That threat manifested in the 2020 protests, which were the largest ever in Belarus' history. These protests began after Lukashenko said that he would seek a sixth term as president, and intensified as many Belarusians were tired of his endless presidency.
Consequently, Lukashenko became paranoid and reckless. Belarusian police arrested Russian mercenaries, surprising everyone, and provoking Russia to ask why their citizens had been arrested. Then a Ryanair plane was forced to land in Minsk after Belarusian security claimed there was a bomb threat. However, after the plane landed, an opposition journalist and their girlfriend were seized and taken off the flight. As Ryanair are an Irish airline, Ireland demanded an EU response, and sanctions followed.
Given this context, it seems likely that Lukashenko was motivated to seek revenge against the EU by using tactics he knew worked, because he is friends with leaders who already have been using similar tactics.