Sevilla is surely lucky because they were playing against Manchester United while manchester united was not in good form and they had many mistakes in the game. After Ten Hag joined this team they improved their performance a lot but still sometimes they get bad results and they have unstable performances, Sevilla was lucky because they played in this situation against Manchester United.
More precisely, Sevilla's luck was due to facing Manchester United, which was in a bad condition because their defender, who was always the key to the defense, was injured, so he had to be replaced by a defender who often played by making mistakes. It was proven that Varane's absence in several matches made them easy to concede goals so they lost in the second leg and could only get a draw except when facing Brighton in the FA Cup semi-final.
Later against Juventus, whose defense is strong enough, maybe they will face difficulties, yesterday they won over Bilbao in the league because their opponents performed worse than them, not because Sevilla performed well.
In the first leg at home to Juventus maybe Sevilla can expect Juve to continue playing as usual tending to defend so that this opponent is not so focused on attack so there won't be many goals scored and Sevilla will catch up in the second leg like they did against United, and progress to the final, although Juve still have a chance to also beat them to advance to the final.