Things get booked up and I don’t believe there was any ill intent in their delay in getting back to you.

Next time if a king bed pops up, I would book it instead of relying on front desk/concierge/the property to switch you. If you dont have enough points to book it while still holding your original reservation then give Hyatt a call. They will modify your original reservation (take off the night that is going to be switched) and book you the king room.