This was a disappoint decision by Judge Cannon. This case could have been dismissed for a number of reason with prejudice, but instead she chose to dismiss it on the grounds Jack Smith wasn't legally appointed. The problem is, the DOJ can appeal this decision, or they can get a legal appointment to take over the case. This may even allow them to convene a grand jury in DC, and indict Trump there, instead of Florida. We'll have to see what happens next.
IMO, should should have dismissed it for selective prosecution, and due process violations, including the invalid order to break attorney-client privilege. She had the perfect opportunity when Hur refused to bring charges against Biden for the same crimes Trump was accused. She could have dismissed the case with prejudice, meaning Trump could never be charged with the same crimes again.
I think the DOJ will sit on this case for a bit before trying to resurrect it. We'll see, but with Biden trailing in the polls, Democrats need something.