The NBA drafts more on future potential than it does on current skill level. So a 1-game hot flash can make a huge impression (show ++ potential) more than a steady series of games. Because of that the NCAA Tournament always produces "fast risers" up draft boards...and then after the Tournament scouts & evaluators go back to looking at the full season and re-even things out.
That said, Wagner & Wilson performing on the Tournament stage against other top skilled athletes with so many scouts watching, will improve their overall evaluations.
Personally, I think Wagner is better off returning for 1 more year of strength training & skill development, but I don't doubt that Wagner will draw some very interesting offers this summer from European teams --- which gives him a larger safety net than most to dabble with the draft.