Why do so many people vote for pro-Russian parties in the...

I often get this question and it deserves a complex answer.
First of all, it's worth making a difference between voters of ANO, populist party of ex-prime minister Andrej Babiš, and more fringe parties that might end up in government with him.
While ANO has moved much more openly towards Russian narratives concerning Ukrainian refugees, European integration or our NATO commitments, it still doesn't dare to openly question Czech membership in EU and NATO.
Voters of ANO are largely non-political, motivated by economic struggles that got even worse in the past couple of years with the inflation and significant rise in energy prices. They're very often elderly and expect significant rise in pensions and other state support from Babiš.
Geopolitical considerations for these voters are almost nonexistent - they might not even reflect on whether Czechia belongs to East or West; alternatively, they might believe our country should be a "bridge" between the two and Babiš managed to make them worried about getting dragged into "foreign" war.
Voters of extremist SPD (far right) and Stačilo (far left), on the other hand, are much more openly pro-Russian in their thinking but they're only a minority in the population - between 10-20 % of Czechs.
Some of them, especially voters of Stačilo, subscribe to old communist narratives and see Russia a friendly power compared to "aggressive" West. They're nostalgic for times of the communist government and especially for relative economic security.
Then there's small group of Panslavic enthusiasts, believing in some sort of brotherly relationship with Russia. They might be influenced by borderline Nazi ideologies and Neopaganism and certainly consume enormous amount of Russian propaganda.
Finally, there's people who fear alleged "islamization" of Western Europe, are afraid of terrorist attacks and threats to Czech "traditional" identity and way of life. These people - often also hateful of sexual minorities - were fed propaganda claiming Russia is some sort of white, Christian and traditionalist society.
I hope this helps to further understanding of this incredibly complicated topic and I'm happy to answer any additional questions you might have.