How much traffic is there likely to be at 9 am on a Sunday morning in January anyway ?
Is it possible there was a screw-up with some roster or someone had a flood at home and couldn't make it to work at the normal time ?
Yes, in an ideal world everything should run perfectly but at a tiddly airport run on a shoestring like MME it's not affordable to have backups for everything.
What was the impact of the 30 mins closure ? How many diverts ? How many movements didn't take place ?