If, as multiple sources report, Russian President Putin has fallen under the spell of Rasputin Patriarch Kirill, the Patriarch of Moscow and All Russia, then perhaps a major motivation for the invasion is that the Russian Orthodox Church wishes to displace the growing Ukrainian Orthodox Church, which only achieved (or, if you prefer regained) its independence in 2019. As the NYT explains,
If Russia wins, the Ukrainian church is unlikely to survive inside Ukraine.
Prizes in the struggle include holy sites such as the Monastery of the Caves, a sprawling complex of churches in Kyiv overlooking the Dnieper River, whose golden onion domes were glistening in the sun on a recent afternoon as artillery shells exploded across the capital. In the caves, in grottos, lie the remains of the earliest saints of Slavic Orthodoxy, control over which would symbolize pre-eminence in this branch of Christianity.