The success of a group is probably closely tied to their understanding of the mission they are on.
The key isn't just explaining which way the group is headed, but why, how, and what rewards are at the finish for the members of the group and the organization as a whole.
I've been on too many projects where details are shared, but none of the big picture items that give the details context. Buy in jumps when everyone understands what the common goal is. The destination is secondary to moving towards the destination.
We are all willing to give great effort when we feel the effort is worth the result. When we don't know the result, efforts will be mixed.
Don't keep the direction a secret. We're not psychic.