I think the key factor here has nothing to do with religion directly. It’s more to do with technology, specifically the invention of the movable type printing press.

Jan Hus and the Hussites introduced several key ideas which the Protestants would adopt, such as preaching in the vernacular language, and an individual’s direct relationship with god rather than through a priest. Luther was greatly influenced by the works of Hus.

However the Hussite religion was regional, it never spread far outside of the bohemian realms. This is a common theme when looking at anti clerical movements before the Protestant Reformation. The other two examples which spring to mind for me is the Lollard movement led by John Wycliffe in England beginning in the late 14th century and predating even Hus, as well as Savonarola in Florence at the end of the 15th century, who was hugely popular and took near absolute control of the city from the papacy briefly.

The ideas of Hus and Savonarola eventually spread throughout Europe, where they influenced many anti clerical thinkers. But they did this relatively slowly, and in perhaps what we’d today call an “academic” way. Luther, whose own ideas can trace many of their roots to his predecessors, was operating just as the printing press was allowing for information to be disseminated at a much faster rate than previously. As a result, when he published his criticisms of the Church, it spread much faster than previous movements were able to, as well as throughout all levels of society.

The real key action Luther took was that he printed a version of the bible in vernacular German. While the idea of teaching in vernacular was one shared with Hus, this act of printing in a language a large portion of the population could actually read completely changed the relationship individuals could have with religion. For the first time they could read the words and interpret the teachings without an intermediary such as a priest. And because of the printing press, these bibles were widely available.

So to sum up, while Hus predates Luther and shares many of the same ideas, he was limited in his influence largely to what is today Czechia. Luther, largely thanks to the advantages of printing, spread much faster, becoming influential across Europe in the span of a few years, and influencing the direction of the whole continent, not just one region.

It’s worth mentioning that Jan Hus is considered the father of the Bohemian reformation. When people refer to the Reformation, obviously they are referring to the Protestant reformation, which is more a rapid collection of reformations across Europe directly influenced by Luther’s criticisms and actions. The influence of Hus on Luther is certainly worth mentioning, but Luther’s portrayal as the father of the Protestant reformation is pretty understandable.