Ukraine has been shelling Russian military installations for months and current government is openly hostile towards Russia, wants to join Nato and Zelenskyy called for Nuclear armament of his country.
Think if this was a situation in Canada. How long would the US tolerate Canadian government being openly hostile to the US. Employing the kids of Russian officials. Asking Russia for Nuclear arms and military aid. And openly shelling Alaska.
The Donetsk region of Ukraine doesn't want to be part of it Large parts of Ukraine are ethnically Russian and voted in past for the pro Russian candidates.
This is a regional conflict with global implications. But the more the world gets sucked into it. The longer the suffering for everyone.