I think Dragon and Roger had a sort of connection before the latter departed. It could be that Dragon learned of the “secrets” of the World from Gol D. Roger in some way and that caused him to “arrive at his own conclusion” which was to betray the World Government and launch a fierce, direct opposition against them.
My guess is that he got his tattoo after he formed the Revolutionaries and then became a dangerous criminal rapidly.
This pushed him to give Luffy to his father Garp to raise him since Garp is trusted and Luffy won’t have any ill connection attached to being around Dragon since there was no known link between Dragon and Garp. This explains why Dragon had this homing instinct without even realizing. He missed Luffy a lot and faced in that direction as an expression of longing for his son. I don’t think Dragon’s wife has a crazy past like being a Celestial Dragon and then getting killed for marrying a commoner, etc etc. I believe she’s a normal woman who was his ally when he first formed Revolutionary Army.
The most intriguing part of Dragon’s actions is when he prevented Luffy’s execution in Logue Town and then after Luffy escapes he says that “the World awaits our answer”.
Which means Dragon has 100% confidence in Luffy achieving his dream which is why now when he learns of Luffy he seems unmoved like he doesn’t care. It’s just that he knows his son is gonna be one hell of a pirate and doing what he’s doing, which is natural for his bloodline. In other words, Dragon knows that Luffy will find One Piece and is waiting for the time when he “arrives at his own conclusion”- Rayleigh’s words.
And when Luffy arrives at his conclusion after finding One Piece, Dragon and Luffy will meet to “answer to the world”. Which is vague enough to be anything.
Rayleigh did say to Straw Hats that he can tell them everything, but that they shouldn’t be hasty and make their own conclusion of everything.
*Theory by AllBlueReverie
