I don't consider it as a good performance from Manchester United. They lost the match at the end is important result and they even faced with a bigger loss if Bayern Munich make their shots better. The final result looks to tight between two clubs but in fact Manchester United found very too late goals which did not help them to make this defeat looks better. If you don't watch the match or the highlight, simply look at the final result, you will think they have a balanced match with Bayern Munich but in fact Bayern Munich dominated the match. In early of second half, Bayern Munich got some opportunities to destroy Manchester United with a tennis result but they wasted those chances.
Harry Kane played in Premier League many years and is a second best scorer in history of Premier League. He faced with Manchester United many times so he has enough experience with Manchester United and understand the opponent well. Beating Manchester United can help Bayern Munich to open a gate to get a first position in this group and can complete their tasks in this group a little bit sooner.
Bayern Munich is a big opponent for Manchester United because these two teams have had a very different balance in recent seasons. Manchester United, which had good progress last season, seems like their performance this season could be said to have dropped drastically because in the domestic league they were not able to put up much resistance, let alone in the Champions League. To be honest, Erik Ten Hag has done a better job since he came to Manchester United, but he has struggled to develop his potential due to not being able to recruit quality stars in the transfer window due to being given a small budget.
Different from Bayern Munich, they were able to strengthen their squad quite perfectly both from the front line, midfield and also brought in a new goalkeeper. I agree with you that Manchester United could have conceded a lot of goals in this match because many of the shots taken by the Bayern Munich players missed long otherwise they could have scored a lot of goals.