Perhaps Haaland felt distressful after some disappointed individual performances when playing with Arsenal last season and after scoring a goal in this match, as well as some situations in the match between two team players, he wanted to take action to release his stress. But either reasons, it's very bad activity that he needs to avoid in future.
You're right because Manchester City had a tough game and almost lost to Arsenal if there wasn't a late goal in the second half. So it's clear that Haaland actions were one of those outbursts that he couldn't stand. I understand maybe Haaland got carried away and didn't think about the consequences, but the media out there will continue to highlight it as a form of reciprocity. I mean the actions and words of a player will be very sensitive given his status as a prominent player in the EPL. Hopefully, in the future he will be able to refrain from acting rashly.
Such things or actions seem to be natural on the field because of course, in the match there will always be emotions created and thus they will also basically be difficult to control. Moreover, when the situation and conditions also allow for players to take such actions but indeed, it would basically be better for them to have a high level of patience so that they can prevent taking such actions. But with that said, I personally don't think it's because Haaland is struggling to score goals but, because Manchester City are also playing at home, it's possible that Haaland is also carried away by the atmosphere that occurs in the stadium with many fans who may also have an impact on players doing so.