It is simple probabilities; it doesn't matter how many engines you have, the risk of losing one stays about the same but if you do lose one on a twin you have lost half your thrust and will probably have to divert whereas on a 4 only a quarter is lost and you will probably not. On a 380 losing one you still can miss all the terrain in the world by a healthy margin. The crew did exactly what any seasoned aviator would be expected to do with a single system failure and what the regulations were designed to allow for.
Using the divert argument above you could have a hundred engines and some would think you should divert when down to 99 and you know what they would be right but only if continuing would have resulted in taking a meteorite strike!
This thread confirms 2 things to me that I already knew; 1. how many people like to pretend to be experts on anonymous websites and 2. how incapable of logical thought some real pilots actually are.
To quote from a dead stick F16 pilot when told his Mayday was number 2 behind a B52 with an engine failure "yikes, that will be the dreaded 7 engine approach!"