Short Answer: Because he wanted to make a clean getaway! ๐Ÿšฟ๐Ÿ˜„

Explanation: The robber took a shower because he thought that by getting squeaky clean, he could wash away any evidence and leave no trace behind. Little did he know that his plan would be foiled by the clever detectives who were hot on his trail! But hey, at least he smelled nice while being caught! ๐Ÿง๐Ÿš”