What are comparable shows?
I, Zombie peaked at 2.29 million
Z Nation at 1.62
If we branch out
The Orville 8.56 million
Most popular Arrowverse show is the Flash, peaked at 4.83
It's possible that we are living in the age of the two most popular genre shows in decades - TWD and GOT. Most popular genre shows in cable history for sure.
That's a strong comment on the interest of TV/fantasy audiences in general; it seems despite some (many who do not even watch the shows, but complain in any case) going on and on about how "bleak" and/or "violent" the shows are (some rail against the imagined "political tone" of GOT &TWD), they maintain the far and away lion's share of interest of TV/fantasy viewers. Nothing else comes close, including superhero series which should have more of built-in audience (made up of members from generations of fans familiar with the characters/situations), but are not.
EDIT: Supergirl probably had a chance to take the crown, being that it aired on CBS. However the show wasn't well received, so the 12.93 million it got for the premiere will remain it's series peak.
But a pilot is not indicative of its regular performance (which is what is considered with GOT & TWD), so outside of pilot curiosity, the drop in ratings is the standard for the series, and its quite low in the ratings comparison.
Eh, I imagine the ZA went differently in different parts of the country and the world. It's not hard to imagine unlikely survivors cropping up here and there, especially with the intervention of artistic license.
So far, whether in Los Angeles, Mexico , Texas, Atlanta or Virginia, the dangers of the ZA seem to follow a pattern of growth and lethal effects, so for a guy who admitted not knowing how to deal with walkers, he should have been killed by now.
The purpose would depend on what was written, and it may or may not be the right move, but if there's no body then there's always the chance of a return.
I sort of think the only way for Alicia to become a stronger character is to know--beyond the shadow of a doubt--that her mother is dead. Not that she should have any suspicion of / awareness of Madison being alive somewhere, but instead, her acknowledging she's the last of her family line is a sobering thought and forces anyone else to step up, take all she's learned and carry on as her mother would have.