Just my opinion but Putin is doing this because biden shows weakness in foreign policy.
Russia does not care what stooge the ultrawealthy and Power Okole puts into the White House. Russia wants their security guarantees from the ever-encroaching US empire towards its borders.
In essence, Russia wants:
1. US/NATO remove any troops or weapons deployed to countries that entered the alliance after 1997, which would include much of eastern Europe, including Poland, the former Soviet countries of Estonia, Lithuania, Latvia, and the Balkan countries.
2. Russia also wants US/NATO to rule out further expansion, including the accession of Ukraine into the alliance, and that it does not hold drills without previous agreement from Russia in Ukraine, eastern Europe, in Caucasus countries such as Georgia or in Central Asia.
It has been an undeniable fact that the US empire has long since been militarily containing Russia and China for that matter. However, the US empire is currently escalating the situation even further in both Eastern Europe and the South China Sea with bogus excuses and baseless accusations of expansion to justify deploying its imperial military assets on the border of both nations and positioning strategic missiles within reach of both country's respective capitals. You actually have to admire the immense patience both Russia and China have displayed in the face of such obvious aggressively evil acts of war by the US empire since the end of the Cold War.
Russia and China are not saints in the least, but it is the US empire that is currently fanning the winds-of-war on this planet.
Russia will invade.
If the US empire does not give Russia its security guarantees,
WWIII WILL HAPPEN, and the planet needs to know what was responsible: the global ambitions of the
US EMPIRE.