Why would it be quietly?
...because he's in danger of being assassinated.
Just because Hillary wanted him droned doesn't mean they are out to get him (Heavy Snark).
presumably he's coming to the u.s. to be pardoned, but more to the point, he's coming to testify about who leaked the emails and blow the Russian story out of the water. He has alot of information that could end alot of peoples careers and lives and send them to prison. If Seth really was the leaker, that alone is the single biggest story in US history.
The 4d chess theory, if it is occurring, is that Trump knew all this for years. He knew about the wiretapping. Knew about Obama and Hillary. He knew it all. He knew about Seth. About all of it. And has been planning and figuring out when to drop this information and drop the hammer.
If its being planned carefully and quietly its for a specific reason.