You might like to look outside leftist (and rightest) rags for explanations.

https://news.uchicago.edu/story/putin-invasion-ukraine-russian-empire-19th-century-imperialism-history

https://www.atlanticcouncil.org/blogs/ukrainealert/putin-admits-ukraine-invasion-is-an-imperial-war-to-return-russian-land/

https://www.rochester.edu/newscenter/putin-russia-invading-ukraine-explained-512642/