I agree with you all on his choice here, I think he could have been well-suited for a South American team, it hasn't harmed Bielsa doing this.
But, if you dig a little deeper perhaps this is a higher-profile role for him because the next World Cup 2026 is in North America, Canada and Mexico??? As a host nation, there's going to be a huge focus and interest in him and his team.
Maybe the fires are burning out with him, the result of some big salaried jobs and payouts along the way, he certainly doesn't need money anymore, so working part-time picking up more multi-million $ job with the chance to make himself a household name in NA during the World Cup and thus more media/sponsorship deals to be had is actually a smart step.