Moose are easy to kill for such big animals but every year people lose them to two things. Improper shot placement and poor penetration. Watch some YouTube videos and pay special attention to penetration, if the arrow doesn't dissapear from sight, I consider it poor penetration. If half the arrow (and often more) is visible it's poor penetration, no question. Seriously, watch some videos
Every time that I've gone after big animals I've paid special attention to my arrows and broadheads. A well set up arrow can "sometimes" overcome the problems encountered hunting. Problems that cause poor flight, poor shot placement, poor penetration etc. Do some serious research regarding your arrows and you'll probably come up with a different combination than most folks believe in.
Take a look at dr. Ashby reports and also look up Andy Ivy, I think he's got some videos on YouTube shooting big animals.