With the new raid and new war campaign. It became completely obvious that this is all part of Sylvannus's plan.
1. Nathanos on the boat when you get the new quest " War is Here" something along the lines (I Didn't record it and my alts aren't on the same page) we need the Zandalari to join us, no matter the cost.. or some shit like that.
2. the Mass of the Zandalari Forces ar emoved to Nazmir with little loss to the small alliance forces.
3. Dal Zala falls and so does King Rasta... So Talajni can take over and forces her to join the Horde.
4. Alliance lose some of their lead characters (This I don't know if tinker dies and what happens to Jaina) but yea.
my thoughts from the horde intro. That this has all been planned out from Sylvannus just like everything else that has happened in BfA.