3. First of all, Harry didn’t battle Voldemort without a crowd.
Very cinematic, but where are the witnesses?
4. It was in front of the whole school that Harry and Voldemort dueled.
Unlike all of his previous confronts, this time everybody can see that Harry kicks Voldemort’s ass.
5. And it happened right after Molly killed Bellatrix.
So Harry and Voldemort were there, not out of sight.
6. And Harry sacrificed himself for everyone.
The same thing Lily did for him, thus preventing Voldemort to kill any of them.