I think Trump's camp studied the Biden-Ryan VP debate of 2012 and saw Biden constantly interrupt Ryan and take control of the narrative. In Trump's prep they had him ready for this and, as has been widely discussed, Biden interrupted first, which was Trump's cue to not let Biden take over. Overboard, yeah, Biden was hanging himself in many cases and Trump's talking over him got Biden out of a jam.
If you were to score the debate, Biden rarely answered the question directed to him so he gets a 0 on those questions. Trump mostly responded and in several cases built good arguments. Trump could be against the Paris Climate Change Accords (which are mostly about the Euros beating up America) but still pro-environment, but other than say "I want clean air and clean water" he just went off on a forestfire tangent. But we don't really have presidential debates so we can score them like in high school.