"During an attack, if a figure ends its movement such that the attacker no longer has line of sight to the target, the attack misses."

So reading this, if I have 5 movement points, I can't attack then go move and hide behind a wall out of line of sight?

You are not reading it right. You can end movement as many times during an activation as you have movement points (and valid spaces to end movement in) for.

The rule is just for the case you lose line of sight during an attack . This can happen due to some command cards (On the Lam) giving a movement point to the target during the resolution of an attack, and the target is no longer in line of sight. A veritable chain can occur with On the Lam triggering Parting Blow, triggering Executor, and Forward Vengeance. So it is also possible other figures move to block line of sight to the original target.