They are so afraid, so desperate for a savior, that they accepted Turalyon's gift without suspicion.
So eager to trust, most never wondered why Xe'ra had such a skewed perspective on Illidan… let alone how she had acquired his memories. They never questioned why she would ask that his soul be placed in her.
Perhaps they saw her as a grieving mother? After all, they had seen her child O'ros destroyed. Dead children were especially effective for causing reason to flee before emotion: his old friend Velen could testify to that. Light's Heart, indeed.
On Argus, he laughs, and waits.