Since the brothers were young they had been interested in aviation. Wilbur's mature interest was first triggered by an article on Otto Lilienthal in an issue of McClure's Magazine in 1894. Lilienthal made gliders. While his interest was triggered, he became a serious thinker about human flight in 1896, when the same Otto Lilienthal was killed accidently during a glider flight. Photo's of Lilienthal and his gliders made this serious interest of Wilbur. Wilbur than began to study bird flight. to study his conclusions more he wrote a letter to the Smithsonian institution in May 1899, asking for more study material. Around this time Orville got as enthusiastic as his brother.
They were tinkerers and inventors who liked to invent mobiles
(it was a passion)
What they did do was to build the first heavier than air craft which flew. Powered flight. Kittyhawk, North Carolina 1903. Lighter than air craft had been around for a long time before that.
If by why, you meant what made them decide to do it, it's human nature to invent things. They saw birds fly and thought why can't man?
becouse they wanted faster transpertation they first found this by paper.
When they stopped getting laid by hot looking females in their area and realized that they needed to conquest new territory (Had to slay some more pussy somewhere else) and knew that walking or driving would take too long.
The Wright Brothers were inventors and we always looking for improvements in existing inventions. They believed that powered flight was possible and set out to prove it.
so that they would be able to fly