Other presidents also extended the power of the executive branch and over-used executive orders. Of course, not to the extreme degree Trump did.
Trump's legacy will be his effective use of social media saturation and his "mask off" approach to rallying his base. Previous (R) administrations felt they had to maintain at least a little civility and be coy about the kind of people they were rallying, and cryptic about the kind of emotions that activated these people. You had to use innuendo and dogwhistles. Trump proved that you can directly preach to people's anger, belligerence, and cruelty, win elections based on those messages, and even maintain your popularity by delivering on your promises with oppressive, cruel policies. This lesson is going to be burned into politics long after he's gone: You don't have to even try to be a statesman to lead government.