Good question. But still, if the tree is collecting sunlight to send down it stands to reason it is exposed to sunlight. And its not like we get a full view of the red line from there. Maybe it's just left or right of majiroa. Or maybe majiroa is on top of the tree.
It is way too large to not be visible. We are talking about a tree that, if located on top of the Red Line, would be more than twice as large as Mt. Everest.
The timing is most likely related to the birth of the Mermaid Princess, which the Roger Pirates knew was not yet born.
The common theory is that the One Piece is the destruction of the portion of the Red Line below Mary Geoise, and all seas would unite in "one piece". This would bring freedom to the people, who now would be able to navigate across the world, but also due to the fall of the World Government. It would also result in the destruction of the Fishman Island, which Poseidon would be used to control the Sea Kings to pull Noah with all fish-men to the surface. The mysterious enormous tree would also be uncovered.
This is likely mostly correct but it doesn't get you anywhere. There also lies a terrible mistake in this theory, and that is that the WG needs to be abolished.
The thing, the WG isn't evil, it's corrupted. But the actual problem are Pirates. There's only one single Pirate crew crew free from flaws, and that's not even the Strawhats. It's the Saruyama alliance. Most Pirates we meet are evil.
Most islands we visited are wealthy. They are allowed self-governance, and diplomacy is encouraged. It's far from a totalitarian system, de facto it is very liberal. Most marines we have encountered are good people.
The Tenryubito are terrible, yes, but most citizens never get to meet one. Sure, they have to pay a tax, which sucks, but again, most countries are wealthy.
The Gorosei care about the stability of the world. We see them talk in private, there is no reason to assume they are lying.
Main reason why everyone sees the WG at the core of evil is the genocide of Ohara, but the thing is that it was Akainu's doing. The original plan was to evacuate everyone innocent. That's pretty nice, the US or Russia do not do this when they bomb cities into rubbish.
The bad things the Gorosei did were all for the sake of the stability of the world.
Pirates, on the other hand do bad things for personal gain.
What the world needs is a reformer, and this cannot be Luffy. Luffy will do what is necessary, but end of the day he is an idiot.
However, one of Luffy's biggest strenght is his ability to forgive, or rather... overlook people's crimes. The biblical Noah was a ship meant to save all the species, and our Noah will save Fishman and Tenryubito alike.
This is all not even close to 10%. Hence why the editors were so confident when they said no one found out yet, despite this part likely containing truth.
