If you have internet phone wouldn't you leave your Wi-Fi on all of the time though? If they woke up in the middle of the night with an emergency they would have to run down turn the Wi-Fi on before they could make a 911 call.
Just thinking that anyone who was going through the house and looking at items for sale might have inadvertently picked up the router and hit the power button. I'm not sure I would find it unusual that it was off after the kind of day this family had just had. Just wondering if LE knew about the estate sale when they started looking for evidence?