The blood elves joining the horde and parting with humans was a perfect storm, a large part of it was definately the aid from the forsaken, I am fully convinced (= read this as an opinion) that if not for the help of the forsaken, the Blood Elves would not have been able to ‘hold the line’ and we’d now be calling Quel’thalas something more along the lines of Northern Plaguelands.
I think absolutely that Garithos played a role tho, sure for us the players its easy to look at the story from a top down perspective where we have all the pieces of the board in view at all times, but what would the average belf on the ground have known? that a human representative of the alliances remnants tried to have the last line of their royal family executed for choosing questionable allies over death by scourge as we see in the missions where first we repair the observatories and then fight off the undead in WC3:TFT
In the same way that helves would look at it and go what do you mean join the horde that attacked our homeland, while whats really happening is that we’re not talking about the same horde, Grommash sacrificed himself for a new beginning and Thrall forged a new path for the orcs, but how is the average high elf exile supposed to know this? the only logical answer is, they’re not.
Therefor I think its actually pretty cool that they show that ingame both sides of the spectrum are sort of right, but only because they don’t have the full picture. I like that blood elves can go BUT GARITHOS at high elves who can then go BUT ORCS back.