Why was Martin Luther translation of the Bible different from people who translated it before him? Didnt they have they have thoughts to appose the Church's practices?

The most important part of Luther's views on language wasn't the translation itself, per se, and his version of the Bible really wasn't that different in terms of content, though there were controversies and meaningful changes (mostly word choices) here and there.

The critical thing was his idea that church services should be conducted in the local language (whatever it may be), instead of strictly regulated Latin, as the Catholic Church stipulated. Though people could memorize Latin passages and psalms, much like non-Arabic-speaking Muslims memorize the Quran, Luther felt that this made it hard for the common man to really absorb and understand their contents. He believed that this smoke-screen allowed the Catholic clergy to distort the Bible's teachings. In his view, a quality translation made with a righteous mind retained all the divinity it needed.

Luther taught that the Bible itself, and not other people's interpretations of it, should be the basis of Christian faith and education. For this to be possible, it had to be directly accessible to everyone in a shape they could understand and study on their own. As you mention, he wasn't the first person to translate the Bible (even into German), but the emphasis he put on its importance caused a steep increase in the amount of other translations being made. The written form of Finnish (which had only existed in spoken form until then), for example, was specifically created for use in the New Testament by a Protestant priest and personal student of Luther, Mikael Agricola. Luther's translation work thus set an important example for others to follow and allowed new literary cultures to grow.

As for Luther's German translation itself, it has been said that it was simply "better", easier to read and more interesting than earlier versions. He paid special attention to how it would work when preached aloud in front of an audience. Earlier translations had been rather stiff, as opposed to his more emotional, colorful approach (while trying to maintain the contents). In difficult cases, he focused on what he saw as the meaning of the text over the exact word choice, which other translations had often preferred. Many Hebrew or Greek metaphors and other phrases, for example, made zero sense in German, so he had to improvise.

Of course, it also got a lot of attention thanks to being written by, well, Martin Luther himself, in an age where printed books were quickly gaining popularity, aided along by his own theological endorsement.

Source:

Luther's Translation of the Bible, by Birgit Stolt