I am well aware of what crew timing out is, but you have a regularly scheduled flight, with a perfectly good airplane, and no other reason for a delay, except the comment that the crew timed out. Surely the schedules would not plan to put a crew on a plane that they will time out on.
It just seemed odd to have a crew time out with nothing else making the flight late. I could see crew timing out if some other issue was making the flight late, but a plane that is ready to go on time should not be impacted by a crew timing out.
Perhaps I am missing something and look forward to you enlightening me with your vaster knowledge!
The flight crew might've worked longer than expected on a previous flight. They may simply not have enough "on-duty hours" (I don't even know if that's a term) left to complete your flight.
Just a guess, but it's happened before. And has been the cause of a
Mayday episode or two.