You can't expect big chain stores to make sense, Home Depot in my area bought a Kmart location in the big downsize with Sears a few years back, and its 2 miles from a main HD store in the same town, reason, keep out Lowes. The store only does OK business, and some of that comes at the expense of the other store, but it does a heck of job of keeping the nearest Lowest 10 miles away.
BTW we also have in Santa Ana a regional sized Home Depot, almost a full city block with just a few non competing stores like Staples in with it. Unfortunately the high traffic means bargains don't hang around unless its some odd stuff. All together I think we have six or eight HD stores within about 12 miles.