Continuity mistake: The Flash is back at Wayne Manor with Batman, after regaining his powers. In the wide shot of the Manor's interior, the windows are about 5 feet in height. The next shot shows the windows now only about two and a half feet in height. (00:45:05)
Continuity mistake: The Flash trips in a field with loads of cacti. One of them changes in appearance between shots. There is also a two foot tall cactus with no branches next to it that disappears. (00:43:10)
Chosen answer: Thawne spent his whole life wanting to discover the speed force. When he did, he became The Flash of his time. But Thawne couldn't live up to Barry's legacy. It drove him mad. And drove to eliminate Barry.
MasterOfAll