The why isn't anything most of us know unfortunately, but I've never once had any QVC package delivered in one or to days. Not when I lived just a few hundred miles from West Chester and not now along the Florida coast. You were unusually lucky I think.
I've been lucky compared to many posters - just had the longest miss of an EDD ever - but by just 2 days. Part of that I'd blame on QVC processing and partly on some obviously time gaps that happened at UPS according to the last few days of my tracking.