He did it even better than you're saying, there's a missing piece that's almost never mentioned: The list of countries in the travel ban were identified in 2015 and early 2016 during the Obama administration, and already had restrictions due to being the most likely sources of terrorism.
Inconvenient truths like that are something I'd be concerned about being kept off of something like WikiTribune by squatters.
If you're going to go back and rest your argument on what the Obama administration did, then you still have to explain why Trump needed to do what he tried to do.
Calling back to the Obama adminstration's actions makes it harder, not easier to justify Trump's EO. You have to explain why the Obama administration's actions were insufficient--which Trump staff did not even try to do. They just asserted that he had the authority to do it, regardless of any proof it was necessary.
The ones where the Supreme Court essentially agreed with him, at least partially? I'd say he got what he wanted, even if with a delay. The goal was curtailing immigration from "bad" countries, and I think that has been achieved by him. And he also consolidated his base by showing that the other side will oppose what Trump's side considers fighting terrorism by any means, including legal tactics that look very questionable to a common person, like arguments "if other person did it, it is legal, but if Trump does it, it's illegal".
> leading to many of the legal challenges being able to hold water
There would be legal challenges in any case, and given how many judges are from the opposing party, at least some of them would succeed at least temporarily. It's unavoidable in any case - what's the point then taking it slow? It would just give the opposition more time to stall.
Could he do it in a softer and more gradual manner? Of course he could, but which one of his goals would that promote? His goals are curtailing immigration from "bad" countries and showing his base that he's ready to act on that and to deliver results. I don't see how soft approach would serve those goals.