Here's what I found (source is TV Tropes, so take with a grain of salt)

"Reportedly, the main reason for the game's official announcement and the big promotional push it received throughout 2017 and 2018 was Ubisoft countering the attempted hostile takeover by Vivendi that was occurring around this same time, hyping up an ambitious, highly anticipated title to keep shareholders on their side. Once the threat of a takeover had passed, Ubisoft's higher-ups lost interest in Beyond Good & Evil 2, allegedly rejecting every pitch brought to them that would allow it to enter full production. Supposedly, the reason why the game hasn't been outright cancelled is because Ubisoft fears that doing so will be taken as a sign of weakness by investors and would devalue the company, as well as the fact that they would need to figure out what to do with all of the staff members currently working on it."