It seemd that the studio owner, who was also the game's lead designer, was accused of inappropriate behaviour by several employees.

Relations deteriorated to such an extent that the owner not only dissolved the employee-led board intended to resolve those issues, but also fired any remaining employees that hadn't already resigned in protest.

At least one of the other indie studios that were contributing DLC characters backed out and the publisher cancelled plans for future updates.

That's my limited understanding from a quick once-over of https://www.engadget.com/505-games-ends-indivisible-development-220350903.html anyway, so please add to or correct that explanation :)