Presumably the same effect that made every fashion designer at every sports shoe company decide simultaneously and “independently” to put the players they were sponsoring in pink shoes during the recent World Cup, despite each of these companies having incentive for their design to stand out.

Ask AI (roughly) the same question; get (roughly) the same answer. Regardless of what model you’re talking to.

(Why? Because every AI company consumes the same whole-Internet corpus and distillations of all their competitors’ models; of course all their models’ answers will converge, especially about anything subjective where they haven’t supplied a specific “right answers for domain X” training dataset to override the “base consensus.”)