Why would you put the performance Murray had in Portland aside? The Hoop Summit has been the breakout game for a lot of players- Dirk Nowitizki, Tony Parker, Enes Kanter, Andrew Wiggins to a certain extent (when he played in it as a 17 year old). Yeah, you exercise some caution judging off one game, but it's not like Murray just hit shots (which can be a come-and-go thing). Murray handled the ball, made passes, made some plays on D, scored on drives to the hoop, and hit shots. It was a pretty full arsenal.
There are a lot of people who've seen both Newman and Murray play (I'm not one of them), because both their teams played in Kentucky this past season, including a game against each other. Newman has star potential, maybe (maybe) more than Murray, but if Newman isn't an option, then Murray is the best possible way to replace him.
It's not like people are just saying "stop recruiting Newman (after 2+ years) and get Murray". It doesn't look like Newman is coming. If that's the reality, then move on to Murray.