This was beyond many people's predictions. Real Madrid, playing at home, were heavily favored and believed to win the match easily. However, it turned out not to be the case. Real Madrid only managed to win by a single goal, despite Osasuna's very defensive tactics. I think Xabi Alonso should have made many changes to the team's play and created more chances, but in reality, he didn't.
So, even though Real Madrid won the match, their overall performance was still quite disappointing.
Before the match some persons had already predicted that Real Madrid will win with ease and without breaking an sweat, I didn't agree with that because some times it's the games that we thought will be easy that ends up being difficult. Yes Real Madrid dominated the game right from the first half but were unable to score a single goal untill the breakthrough came through a penalty and even after that, it was expected that the goals will start pouring in, at least 2 more goals but it didn't happen that way. A scrappy 1 - 0 win was enough to get all 3 points though. The team still needs improvement.
You are right, most fans expected Real Madrid to beat Osasuna by a huge margin, but it was not easy. The match could have ended in a draw if they had not scored from the penalty. I watched the match at full time and Real played well and kept the ball for most of the match and played attacking football but they did not score. You play well all the time but if you do not win then that good performance is worth nothing. Real won their first match of the season in La Liga, it's a good start for them but they need to improve a lot because they will have to fight against strong opponents in the upcoming matches and win.