Epic Games*, Mihoyo**, IO Interactive, Bethesda/ZeniMax***, Deep Silver.
* Epic games is 40% owned by a publicly-traded company, Tencent.
** Mihoyo filed for an IPO in 2017, but withdrew its application for unknown reasons.
*** ZeniMax Media was recently acquired by Microsoft, and is now a Microsoft subsidiary. I’m not sure if this makes it count as a ‘non-public gaming company’ by your definition.
From what I understand, history has proven otherwise. Wars are always very profitable for certain groups.