I'd be cautious about making the causal links there.
Penney's problem was in full evidence before the two-mommy thing. The decision to break the stores into "boutiques" did huge damage to the shopping experience. A busy shopper popping in to buy a bra or panties found they had to browse the whole store to be able to see more than one brand. Those items were spread all over the store..bras here, there and over yonder instead of all in one rack.
K-Mart was in the dump before Sears Holding took over, and K-Mart was then no longer a "flagship" store like Sears. The stores fell into disrepair from lack of maintenance budget, and were sold off if they were within 10 miles of a Sears (which is also failing due to no political fault at all).
Then there's the overall failure of shopping malls because of crime. That hit all three pretty hard.
We're fooling ourselves if we believe conservative boycotts cased the failures
When Tom Selleck went on Rosie's O'Donnel's show to promote his new movie, she went aboard him with a firebrand over his making a pro gun ad for the NRA. He never even got to mention the new movie during her anti gun, anti RKBA tirade which consumed the whole spot Selleck appeared in in her show. Seriously offended, a grassroots groundswell of gun owners basically told K-Mart (for whom she was a designated spokesperson) "Either she goes or we do".
She didn't and a lot of gun owners voted with their feet, me included.
Prior to that, K Mart was the nation's single largest volume gun dealer, and did a rollicking business in sporting goods.
After that, not only did their firearm sales drop hard, people who had gone there who had an alternative, usually WalMart, went elsewhere for other things, too. So, Mom and the kids didn't shop while Dad was looking over the 'guy stuff', at least not at K Mart.
That was long before Sears and K Mart got together (we still had a K Mart here), back when Clinton was Potus. Martha Stewart's Housewares line probably didn't help, either, while the stuff was of reasonable quality, the color palette left much to be desired, all before she went to the hoosegow.