In any category, light buyers (i.e., those who only buy the category occasionally) favor large brands over small ones. This is known as the “Natural Monopoly Law” (i.e., larger brands monopolize light buyers).
This is because light buyers are less aware of the different options in that category, and they will just “default” to buying the brands that immediately come to mind–in any category, these will be the large brands, because they can spend a lot on advertising (see marketing must build availability). This, in turn, leads the large brand to grow even larger, in a virtuous reinforcing feedback loop.
The inverse of this law is also true: because light buyers favor large brands, any brand that wants to grow must target light buyers.