You've fallen for the usual Western narrative that "Putin is a threat". They're using Cold War tactics to make people think that Russia is an evil expansive country. All Russia wants is security.
Tell me,how many countries has Russia invaded since 1991? And how many countries have the US invaded since 1991?
Now Ukraine,then Poland is a speculation. Poland is an majority ethnic Polish and Catholic. Ukraine has a large Russian and pro-Russian speaking population and it's been a big part of Russian history.
Ukraine is bordering Russia and has ports in the Black Sea. If Ukrainian became a member of NATO or had any kind of military bases there,any ballistic missile or army could reach Moscow and the Don and Volga cities.
They cannot allow this. They don't want Poland and they don't want the Baltics. They want NATO to stop arming against them all the time.