You do need a goal of course, especially when you are Real Sociedad and you play at home. If you don't score in the first game, the probability that it ends with a draw and you still are well situated for the second game is too low. Real Madrid wanted this one goal and anything but a magical night for Real Sociedad will inevitably lead to losing the second game or at least not winning it, which is still sufficient for Real Madrid.
Many are praising Real Sociedad's performance. And they think that Real Sociedad has a chance to qualify for the final. Real Sociedad has a small chance. Since football is always unpredictable. However, if we compare the overall condition of the two teams, I would say that Real Madrid will easily qualify for the final.
Real Madrid won in Real Sociedad's home match. Although Real Madrid could not win by a large margin, Madrid won. I do not think that Real Sociedad will win by a large margin of 2 goals in Madrid's home match. Ancelotti is a very experienced coach. So he will try to draw the second leg match. I would say that Madrid has a high chance of winning in the second leg match, but if Real Sociedad plays very well, the match will be drawn.
Hm, this is why there are odds. Yes it can't ever be 100% safely predicted because otherwise bookmakers wouldn't offer a 1.01 on some favorite winning the game as there is still a tiny tiny chance that things go against expectations. But to a certain degree it is predictable and Sociedad need a draw in my opinion to somehow have a chance to win the game with the help of either going all the way to the penalties or through counter attacks because Real Madrid has to open up their defense in order to put up pressure against Sociedad. But now Real Madrid can play counter attacks with Vini Junior and Mbappe and I think there is harder thing to do than defending against counter attacks with those two guys. That is why in my opinion the small margin they won the won the first game by will be enough here.