How is it you don't know? seriously how do you not know why the Gods left.
We got attacked.
12,000-15,000 years ago the enemy set up a spiritual attack everyone even the Gods and Higher ranking humans could not stop it. So the Gods spent their time removing things from this World to prevent the death, destruction, and capture of stuff.
For example Plato states Atlantis is in the Atlantic ocean which is wrong Atlantis is a section of Heladiva(Sri Lanka) and Indonesia i.e. Indonesia is the outcroppings of Atlantis region. But he does state something correct, the explosion at Atlantis most likely caused by enemy extraterrestrial magick and not by crazy humans doing experiments and trying to destroy the World "Oy gevalt humans are crazy" like mainstream kosher supervision new agers state. According to Plato occurred sometime around 12,500 years ago or around 9600BCE. He was right about the date but wrong about the location.
Non the less Atlantis was probably a targeted city by the enemy magickally and probably through enough of civilization magick they blasted Atlantis. After all Atlantis is probably one of the birthing points of humanity as originally Sri Lanka or Garden of Edin was the location of the first humans. Albeit despite the fact we believe there is evidence that the black race came first, then Asians, then Whites. In my personal opinion I believe Whites were first constructed in a small batch and raised by the Gods to see what kind of potential humans have. After all Adapa is probably one of Satan's eldest son and so fucking advanced in all ways like his father who raised him plus including Lilith. Albeit we don't exactly know who the mother progenitor of the White human race is, it COULD be Lilith. Despite the fact Sitchin lies and creates a whole retarded story about the Gods, the fact he states Nirhursag is also another potential mother or mothers. It's a possibility Satan might have had many female "mothers" give birth to various lines of descended humans.
With that said like Lucifuge Rofocal's people they numbered about 50 people when Satan discovered them some 10,000 years ago. That is perfect to eliminate or reduce genetic depression or genetic issues of inbreeding. 500 people is needed to avoid elimination of the species due to some not reproducing. But because the Gods don't raise humans to be losers everyone reproduces at some point or is allowed to reproduce at an appropriate point. So in essence for species 50/500 reproduction is needed but not for species capable of elevation to Godliness due to the Gods teaching humans and raising humans appropriately that eventually everyone can have an offspring and if they don't want to reproduce they can always do it later on a more appropriate astrological chart level.
So basically 12,000-15,000 years ago magickal reptillian/grey assault came in and then 10,000 years ago the imposition of their attack with Phaeton's destruction using a planet buster, nuclear strikes on various moons, planets like Mars and our Moon, various nuclear strikes across the Earth even to this day still radioactively poisoned like the apartment in India which caused mutations and rad sickness to people i.e. cancer. As well as plasma thermal lances and other destructive weapons. On top of that spiritual assault i.e. coming in astral projected reptards and greytards threatening people and as well as physical assault and physical killing of spiritually advanced people.
With that said the enemy for some specific reason retreated and left a skeleton crew on the Solar System. My best guess is the Gods attacked physically and spiritually and could some how leverage their advancement to prevent the enemy. Another possibility the enemy knew it was a long shot they failed and thus said just maintain the status quo and keep the Gods busy to waste their time and effort on these lower civilizations. My best guess is the jews or kosher supervision species i.e. trick species is just a time waster for the Gods i.e. prevent humanity from advancing and kicking back. Basically mental, physical, spiritual, and technological time wasters and evolution stoppers.