Comment by geoka9

The only reason Russia has been reluctant to formally annex territories it broke away from other countries until 2022 was minimizing economic damage to itself. They knew how sensitive the western countries were to forceful changes of the world map, and felt no need to inflict economic sanctions on themselves for a mere symbolic act of annexing a territory they already fully controlled.

Once that Rubicon was crossed (sanctions were in place and there was nothing to lose), they annexed the four regions of Ukraine that they partially controlled.