It is fair to say that Henry VIII, the Calvinists, and the Anabaptists were intent upon splitting from the authority of the Catholic Church. Luther, however, desired to reform the church; otherwise he would not have written theses for the purpose of attempting to bring the church more in line with the truth as found in Scripture. It was only when the Roman church chose not to reform, and declared Luther to be anathema, that Luther had to choose between the Roman church and the Word, and he chose the Word.
Yes, Luther started out trying to reform the Church, but did not end up there. He stuck with his interpretation of Scripture, and thus created a split rather than reform.