The whole purpose of their job is to protect - not to protect when bugger-all is happening, that would be kind of pointless...
A sign of successful protection is when ‘bugger-all’ is happening.
If they decided to evacuate, why didn't they take him with?
They may well have. Gadaffi may have expected to be carried or something. He would have been an entitled pain-in-the-butt. This was on open ground (desert) and NATO jets would have been after them because they had Gadaffi (the target). How long would they have lasted with the prime target with them?
Back to my original point. They could die meaninglessly. They chose not to. Without Gadaffi they stood a chance because NATO wouldn’t pursue them. Survival was at stake.