This comes from the reliable french game journalist "Gautoz" who heard from multiple devs at Ubisoft Montpellier the news.
Internally, the fate of the game was already decided a few weeks after the release of the game, it was clear in Spring that after releasing a few DLCs and Cosmetics it would be the end.
A few members of the core dev team fought to get a sequel greenlit which did not happen, then they pushed for two expansions hoping that it would work this time but it didn't since Ubisoft needed more hands to help on other projects that had a better sales potential which wasn't the case with Lost Crown not meeting sales expectations.
Another crazy justification that the dev team received from higher-ups was that releasing a sequel for the game would cannibalize long term sales of the first game.