The last minutes goal for Liverpool was a shocker to Newcastle at the moment they had thought it was all going to end in a 2:2 draw, a result which would have favoured Newcastle the more because they were playing a 10 man team. Scoring 2 goals with a red card against the defending champions Liverpool, I think Newcastle actually tried and should be applauding for that. The Liverpool defense too wasn't looking good which was why Newcastle could have gotten those 2 goals, which is something that should catch Arne Slot attention to find a solution for that this season. It wasn't a convincing win actually.
I actually didn't expect Liverpool to win in this manner, and it was a valuable surprise for Liverpool.
Newcastle did look stronger defensively, but the advantage of playing at home gives the players more confidence.
I agree that Arne Slot should pay attention to the defense, which is currently conceding more goals. Even against Bournemouth, despite Liverpool winning, they still conceded two goals.
If Arne Slot doesn't fix this problem, I believe Liverpool will lose their upcoming match against Arsenal.
Events in football are unpredictable and it should be taken as one of those games with interesting outcomes. And you are right about Newcastle confidence in the game being influenced by their home advantage and in front of their massive fans cheering them up. Liverpool defense could be a problem for them when they meet Arsenal in their next game, liberpools defense can't measure to that of Arsenal and if both teams attacks gets offensive then Liverpool might have to concede more.