User blog comment:JMOfficial/Flash Big Bads in the Future/@comment-26618197-20170817204320/@comment-24152851-20170821203728

Ah you see, you didn't get the whole story. At first Eobard wasnt trying to be better than the Flash, he wanted to be a hero like the Flash. But then he found out history stated he was destined to make him Barry's arch-nemesis. So with that revelation he went off the deep end and decided to embrace what fate said he would be, aiming to be the greatest arch-nemesis of all time.

So why is Eobard so arrogant? Because he's following what history said he would be.