I actually like Crowder's chances. He's been getting a lot of respect around the league, being called a borderline All-Star and what not. I think voters actually like guys like him.
Contrary to what some people, like Big333223 right above me, say about undeserving superstars on the All-Defensive team, I think this is rarely the case. Just in the past few years we've seen guys like Tony Allen, Patrick Beverly, Andrew Bogut, Andre Iguodala, Shane Battier, Thabo Sefolosha, etc. on the All-Defensive teams. These are all guys who were averaging less than 10ppg when they were selected. I think the voters love these types of guys, and know voting them to the All-Defensive team is the only time they'll ever be able to get respect as they'll most likely never be an All-Star or win All-NBA, MVP, or SMOY. I actually think not being a superstar sometimes helps you get selected to All-Defense, I don't think the bar is as high for non-superstars.
Also Smart and Bradley might split the vote at the guard position, while Crowder doesn't have that same competion (if a voter was looking to reward a C for their great team defense).
For reference, last years All-Defensive teams:
1st
Tony Allen
Draymond Green
Kawhi Leonard
DeAndre Jordan
Chris Paul
2nd
John Wall
Tim Duncan
Anthony Davis
Jimmy Butler
Andrew Bogut
I wouldn't be surprised to see Tony Allen, John Wall, and Tim Duncan drop off, and questionable on Butler. Also don't think LeBron will be added in. I see some available spots for Bradley, Smart, and Crowder.