Haha, nice one. Although I don't get it.
Okay, their job was a failure because:
All 5 idiots sat in the same taxi, so there was no space for the customer!
Okay, that's not funny.
And, then. Here's the 2nd part.
The 5 idiots decide to open a car-repairing shop. why wasn't there any customers this time, too?
Please give a try and tell me what you think the answer is. ^_^