There were several reformations before Luther. Bible was translated into German and other languages before Luther. Mentel Bible was on it's second printing when Luther started his reformation. Several other successful reform movements started at the same time or little later.
Question is why reformations started at that particular time and why Luther was so successful and several reformations before him failed.
The answer is technology. Printing press revolution had exploded. There was over 1000 printing presses throughout Western Europe when Luther started his reformation. Germany and Italy were the main centers. Pamphlets from reformists spread around like wildfire and the movement was able to grow much faster among common people.
https://blogs.qub.ac.uk/medievalforum/2015/08/19/literacy-an...
>Between 1516 and 1546, 3.1 million copies of Martin Luther’s works were sold in Germany (excluding whole and partial Bible translations). Considering that each reprint had around 1,000 copies, that equates to 3,100 editions of his work alone. Over this period, 1,057 editions were published in Wittenberg, 490 in Augsburg, and in comparison, Basel produced 131 editions. On a shorter time-scale, the number of pamphlet editions produced from 1518 to 1529 is as follows: 181 in Wittenberg, 140 in Augsburg and 61 in Basel. What is more remarkable is that Luther also authored 20% of the 7,500 cheap broadsheets printed between 1520 and 1526. Besides preaching, the Protestant reformers clearly published a large amount of material to disseminate their ideologies to a wider audience.