The Walking Dead: 5 reasons why Alpha didn’t send the walkers
#4- No Message
Whenever Alpha acts, she makes sure that her actions carry a message. If the walkers that have been showing up in Alexandria and Hilltop were dispatched on behalf of the Whisperers, Alpha would own up to it because she would want the message to be loud and clear.
When asked if she sent the walkers in “Ghosts” she made it clear that these are not her walkers. She had no reason to lie, so it’s reasonable to believe that these walkers are not members of the horde.
#3- Fire, Fire Burning Bright
The most obvious reason that massive waves of walkers inundated Alexandria is that they were moving toward the fire. While the fire has been extinguished for some time now, the herd moves in a single direction until something else distracts them.
What was clear from “We Are the End of the World” is that the walker herd lost focus when the satellite flew through the sky. They became distracted, and all it takes is a group of walkers to start moving in one direction for the rest of the herd to follow.
Between the bright light of the fire and the sound of the falling tree, the walkers had something to guide them and given the timing of those two events and the arrival of the walkers it makes much more sense that this is why they arrived when they did.