People are forgetting that We are still in Elbaph Arc, meaning Everything We are getting Exposed to currently is Tied to Elbaph Land,
Pirate World changed in Last 100 Years, but for the 700 Years before it, Piracy was mainly represented by Elbaph & Elbaph Alone,
If Davy Jones Name grew that much & endured all these Years, it's because Elbaph Pirates made sure He will always be Remembered as They spread their Piracy Culture, (Other Pirates existed in Low Numbers before 100 Years, but most of them out of need or circumstances, it was only Elbaph who did it just for the sake of it),
After that, We remember that Xebec wanted to Ally with Elbaph, spending almost his entire Pirate Career trying to convince Harald of such Alliance, why? (I mean the reason from Oda's Perspective) Because He is following in Jones Footsteps, it was Alliance of Davy Jones & Elbaph Ruler that eventually led to Jones Legendary Run, which allowed him to become like a Pirate God,
Why both Giant Pirates Crews have Two Captains? Because it's a Tradition, They are following an OG Duo. In The Past, I thought Elbaph have Two Rulers/Kings, but after this Arc & Flashback, it's obvious that OG Duo were an Elbaph Giant + Non-Giant,
This Giant is Named "Elbaph", The Island is named after him, and their Fighting Style is a Reference to him (Spear of Elbaph),
Elbaph's DF was also his DF & that's why it's a National Treasure, while Second DF mentioned by Xebec, is the One that Davy Jones had,
Now here is the Interesting Part, We have Elbaph (Their God, not the Land), and Davy Jones, and Imu,
Who does these Three remind you of?
Let's add another Hint, Davy Jones literally lived Usopp's Dream & how He wishes his Pirate Career ends, so who does this Royalty Imu living in a Castle above a Mountain represent? She is literally similar to Kaya, (Who was Targeted by Kuro, The Devil in Disguise...)
Let's add more Hints, Elbaph God belongs in Heaven World, and this Mu Devil can possess People, and Davy Jones was said to have been sent to Underworld because of Devil? Does it ring a bell?
Didn't get it yet? Let's see how Oda made it even more obvious, what is Elbaph Tree called? Adam
And what about the other related Tree that is hinted to be somewhere near Mary Geoise/Red Line? It's called Eve,
Do you get it now?
Story of Elbaph God, Davy Jones & Imu (Who got Corrupted by Devil) is literally just Oda's take on Adam & Eve's Story,
Meaning this Devil is Possessing Davy Jones Lover from Mary Geoise (Who I also theorize is Joy Boy's Daughter or Related to him), and He used her to Ruin Davy Jones Alliance with Elbaph God, who Banished him from Heaven because of it,
So to answer this thread's question:
"Davy Jones was Banished by Elbaph God, because of Mu (Devil) who took over Davy Jones Lover & WG"