Then in the 1980's Sears started reducing the quality of the appliances and started trying to get out of repairing those appliances under warranty. They lost a ton of Gen-X and beyond who saw their parents cursing Kenmore.
Then in the late 1990's Sears started reducing the quality of Craftsman. Again Gen X and beyond found themselves or their parents making disparaging remarks about screwdrivers that had such soft tips they were worthless, ratchets whose mechanisms couldn't be trusted, sockets that split down the side, items that were discontinued, etc, etc. Tool Department employees got a God complex about handling or even denying replacements as they deemed fit. The warranty was the only reason to spend the money and it became worth little. Competitors stepped up their game and stole that business.
Somewhere along the way the "fashion" became "thrift shop" and Best Buy was a lot better place to shop for electronics. In many towns KMart was the only place to shop, knew it, acted like it. Target and Walmart came and shoppers were happy to be free of a KMart's inflated pricing and poor service.
Catalog operations were shut down right about the time some guy named Jeff had the idea to sell books on the Internet. Then other stuff. Then everything. But Sears had already destroyed its reputation there again with poor service (I remember waiting FOOOORRRREEVVVER a the catalog counter countless times with mom) and pricing higher than newer competitors.
These decisions weren't all on the back of the various CEOs at the time. Middle managers, analysts, buyers, and even retail employees are all to blame for various aspects.