Pretty sure Trump has demonstrated over the course of the last couple of years that he has absolutely no loyalty to anyone or anything other than himself. The legal process is already underway in the US with a grand jury already taking testimony. Why would Trump stand in the way of that?
as others have said, that's not true
https://www.nytimes.com/2018/11/16/us/politics/trump-administration-assange-wikileaks.html