Before Chapter 1044, people had no idea that Luffy would have one of the strongest Devil Fruits in the series.
The Hito Hito no Mi, Pattern: Nika is the only Devil Fruit power that the World Government wanted to erase from all of history. It allows the user to transform into the legendary “Sun God” Nika.
So we learned that Luffy has this legendary Devil Fruit ability that Joy Boy once had. This Devil Fruit was so powerful that it’s almost a Toon Force ability that gives Luffy the freedom to do almost anything he wants.
The concept of Sun vs. Darkness has already been highlighted in Blackbeard’s previous battlewhere Ace presumably used his Awakened Logia via Entei and covered half the island with his fire, that his ability felt like an island-sized Sun.
In fact, before Chapter 1044, people were still saying things like Luffy’s Haki is more important, not his Devil Fruit ability. But Oda proved these people wrong. After Chapter 1044, One Piece gives the main character one of the most powerful Devil Fruit abilities, with the concept of the Sun God.
Luffy now has the ability to do almost anything he wants, with more freedom and more power once his power awakens. And Blackbeard is the only character who can counter that freedom and power, with his darkness that can turn everything into nothingness.
It makes perfect sense that Blackbeard specifically sought out the Logia of Darkness, when there are other powerful Logia abilities in One Piece. It was probably to counter some absurd and very powerful Toon Force type ability.