The human race was a species with great potential, but it was unable to reach beyond its primitive past. Had it been willing to admit that it was just another animal driven by instincts, it may have fared better. But instead, it insisted on distancing itself from the other inhabitants on Earth, thinking it was better, and creating god images to confirm its superiority. It thought itself intelligent, and measured all other intelligence by comparing it to its own. Had it been as intelligent as it thought it was, its extinction may have been unnecessary. A warlike species it created excuses for conflict and destruction everywhere it went. It fought over many matters of a trivial nature: god images; resource distribution; even the colour of its skin.
In its arrogance, it regarded the Earth as its property, to do with as it wished, without any regard for other inhabitants. It pushed the biological systems of the planet to breaking point. This one species was the primary cause of the sixth major extinction event, and it was directly responsible for more damage to Earth’s biodiversity than any other species in the 4.5 billion years of the Earth’s existence.
But as you know, the actions of humanity did not go unnoticed. The Galactic Community met to decide the fate of this species and came to a decision; until the human race was able to prove that it was worthy, it would not be allowed to leave the planet of its origins. The destruction wrought by humanity could not be allowed to spread into the universe. But, as the Earth approached a tipping point where many more species would suffer, stronger measures had to be taken; the human race was reclassified by the Galactic Community as a disease. Like any pathogen, it had to be contained, studied, eliminated.
The Sol system was declared a forbidden zone. Placed under a strict quarantine with penalties for unauthorised access. Only individuals chosen for their knowledge of dealing with invasive diseases were allowed to visit. The concerns were real, the danger imminent. The human race could not be allowed to spread.
Yet still it persisted, launching its primitive craft into space, intending to colonise another planet. Many argued that it was time for further action; containment was not enough.
The treatment of Earth took place shortly after, and once humanity had been eliminated, the planet began to recover. A few humans were kept alive in heavily secured laboratories for study. There is hope that one day, a vaccine may be developed in case of another outbreak of this terrible illness.