Salah had pace to go along with his talent though, on top of that improved his finishing last season with Liverpool. Not to mention he played under some good coaches which probably helped him.
Shaqiri never had the pace and never scored a lot of goals yet teams continued playing him as a striker, winger or a forward.
Being a ball hog, failing to read the game & not developing are his fault but its also the fault of all the coaches he has had over his professional career that never tried to raise his game or play him in a position that fits his characteristics.
Personality may have a lot do with it as well, Salah seems like he was willing to improve and learn, maybe Shaqiri went against what coaches tried to help him with if they did indeed attempt to. You never know really.