Well most of it's active life has already been done on Switch/PC. No problem here to get some interested Xbox players into the party. Though it seems to me Square Enix received a good check from Microsoft to make the port happen. Also, this could mean the game might come to the PS4/PS5 sooner or later now.
Why do you think Microsoft put a check?
Glad more people can play it now. The same could happen with other SE Switch exclusives, like Bravely Default II (and the entire series, for that matter) and the future Triangle Strategy.
Because the devs/publishers aren't the ones paying to get their games onto Gamepass. Also, we know by demographic,tendancies and sales statistics that JRPGs are more popular and viable on Sony's platform than Microsoft which is why seeing a port of Octopath Traveler on Xbox first before the PS4/PS5 definitely make it hugely possible that Microsoft had their money involved into this.
Anywoo, the same will happen to other SE Switch exclusives in a matter of time after the exclusive deal has waved out. Though can't say if it'll be only on PC or every console thus far since we only have Octopath Traveler for example here.