A double isn't an easy feat, and Galatasaray has literally 1 point to do that. If they get a tie, or a win, they are going to win the league this weekend, and that means we are going to see them reach to a point where they won a double. The comparison is that, Galatasaray won the league 24 times, which is a great achievement, before this season, and only did a double in 6 of those, goes to show how difficult it is normally to do something like this. They won it about 7-8 years ago too if I am not mistaken from my research.
Nobody else did it as much as them and even they have done it so rarely. Usually, the team that wins the league, ends up being in European competition too, so the cup is the first one to not care, and that's why it's very tough to win both.
Also, the Turkish Cup is often overlooked as the last option, as there are also Champions League or European Cup matches. That's why it's not always easy to win two cups. Undoubtedly, Galatasaray achieved a very important success this season. Osimhen was the star of the season, everyone accepts that, but Okan Buruk has also achieved a lot. I think he was sometimes criticised harshly during the season and he didn't deserve it...