Taking 50% of online shopping share because your product is that much better than the competition is totally different than there are no other options. Imagine

Taking 50% of online shopping share because your product is that much better than the competition is totally different than there are no other options. Imagine you have 1000 stores all on the same street and one is so much better than the other stores that 50% of sales happen in that one store and there are no shenanigans where that one store is disadvantaging the other 999 stores. How can you argue that that is a monopoly?