How you finished the game so soon?
Even if its quite smaller than FO4, you need serious time to explore the places. Unless, if you see the green map-mark and you sprinting towards that and you super-fast running here and there to continue further the quest. Sorry, but this is not a "RPG-like" gaming style, this is a... Fortnite style, to run like hell and kill the objective target.
Personally, I'm super slowly exploring the place, I love the alien-extra terrestrial places' look and I want to see more, to explore all the place, etc.
That's why it takes me MUCH LONGER to finish a quest (and I'm always finishing the SIDE-quests, leaving the main always last).