Less scale, easier to fill gaps, less impact

Walmart has basically always been superior to its competitors at logistics. It has been one of their key competitive advantages for many decades. They have been a data monster heavily focused on logistics for most of their existence (I've been reading about their various logistics advantages for 30 years now).

Even if doing a thing is good for a competitor, that obviously doesn't mean that competitor will do said logical thing. Companies fail all the time because they're incompetent in one form or another (or many forms).