@David8260 The way it works is that the first guest to pay gets the booking. "Someone" didn't override anything- it's all an automated system.
I'm guessing that what happened is that an Instant Book came in while you were waiting to pay. That would be instantly confirmed by the system, nothing that the host has control over.
And hosts don't send you an "invite to book". They either accept your request, or pre-approve your inquiry. I suspect you sent an Inquiry, rather than a Booking Request? A pre-approved Inquiry does not block the dates for you- you have to go on to book if you want to be assured of getting the reservation.