That player already did enter the market, and they flopped.
When the galaxy note took off, Samsung responded by also introducing a galaxy mini series in the mid 2010s. It was discontinued after two versions.
In the early 2020s, Apple responded with an iPhone Mini that was similar in size to the phones they were releasing a decade previous.
It was discontinued after two versions because it reportedly only made up about one percent of iPhone sales.
When Apple finally discontinued the dated iPhone SE design and replaced it with something bigger, it reportedly sold twice as many each quarter, despite costing significantly more.
There is no small phone market disruptor coming. Most you can hope for is that maybe Apple will eventually make an iPhone flip