The term alt-right was coined by people who wanted to apply the term to themselves, and it described a contrast to the sort of Republicanism that started to end

The term alt-right was coined by people who wanted to apply the term to themselves, and it described a contrast to the sort of Republicanism that started to end around George Bush Jr, but people just didn't realize it yet. At some point the alt-right became the mainstream right and the old-school Republicanism represented by the likes of Mitt Romney are now the fringe Republicans. When the old guard ages out of office, it's young blood like Matt Gaetz and Marjorie Greene that replaces them.