Without a coherent, plausible, inspiring vision, a team default-diverges.
People aren't diverging on purpose, they just don't know what the vision is.
The path of least resistance for a bit of work will go in some random direction.
As everyone on the team follows their individual path of least resistance, everything tends to decohere.
But a plausible vision is like a magnetic force; things pull towards it unless they have a strong reason not to.
It becomes default-cohering.