Memphis has lots of interest in Donovan Clingan, and in this trade they trade up to #3 to get him trading away next years first round pick (top 10 protected) and a distant 2nd round pick.
Houston doesn’t have a big need for another high upside rookie and is focused on making the play-in/playoffs next year. not only does Malcolm Brogdon fit great and help them win more games next season, the Rockets still stay in the lottery with pick #14, while also acquiring pick #34 in the 2nd round.
Portland is in the infant stages of their rebuild, so getting value out of their veterans (Brogdon) and collecting future assets is the top priority. Portland essentially trades Brogdon and pick #34 to move up 5 spots in the lottery (from #14 to #9) while also picking up a future first round pick in a much better draft.