They EVENTUALLY invited Russia when it was explained it would make no sense not to. Face save attempt. Russia offered a ceasefire at the time if Ukrainian troops moved away from the new Russian areas, and agreed not to join NATO. Harsh, but maybe a counter-proposal would have been an idea...
The bottom line is, it took Zelenskyy 19 months to organise the first peace summit. In retrospect a better move would have been picking up the phone and talking to Russia - which could have been organised in a few minutes.
