No one was "thinking" anything. The system automatically made the change based on whatever the algorithm told it to do, as AI is not always strong on the I. Due to a recent flight time change on an upcoming UA itinerary, my 2 hour connection became a -3.5 hour connection, which is considerably less plausible than your situation. It was a very simple fix to just contact the airline, who was happy to move me to the next flight out. I did not even get an email about this change, and if I hadn't caught it while checking on a different flight, it probably would not have been changed until I went to check-in, because airlines do not typically have humans monitoring these things proactively. Simply contact the airline and get it straightened out.