That's like saying that a machine gun wasn't more deadly because we already had rifles. Trump made a number of major expansions in claims of executive power: spending money which Congress had allocated for different purposes, claiming immunity to legal investigation, using the DOJ to defend him against civil suits predating his run for office, simply putting people in positions which require Congressional approval, claiming that he could override state health authority decisions related to the pandemic, trying to zero out taxes which he doesn't agree with, etc. He didn't get away with all of it but that Unitary Executive theory is a really big shift away from the American system of government and it happened by fiat rather than some kind of reasoned legislative process.

Put more simply, Trump managed to find a position strong enough that he lost the support of even John Yoo, who felt that the President had authority to order torture.

https://www.npr.org/2017/02/08/514049685/former-defender-of-...