Humans, are they really that dangerous?

For countless years, the Intergalactic Alliance put a ban upon Earth, a place where a branch of humans lived.
They were labeled as highly dangerous, and shall not be interacted with.
This label came from a highly important researcher of the Alliance, whom ran simulation on everything and everyone, and deduced that this planet will bring the end of the Alliance.
But as the governance of the Alliance changed, so did its policies, and questions about old decisions were made.
“Humans, are they really that dangerous?
They seem as a good addition to our Alliance, with their flexible thinking, and huge population.”
The new ideas were as such.
And thus, the ban was lifted, and contact has been made.
That was the beginning of the end.
At first, it was awkward.
Humans were wary, while the Alliance’s representatives couldn’t understand their wariness.
They came bearing information on how to solve all the immediate problems of the planet, such as famine, diseases, natural disasters…
And yet, humans weren’t ready to trust them.
They did accept everything, and as soon as they verified their veracity they used them…
But the leaders were using these advancements in a weird way…
They weren’t free for everyone, even though the humans called them “cheap”…
And it even seemed that some countries thought that the fact that the Alliance, broadcasted this information, making it public was a “bad move.”
But nevertheless, it seemed that the choice was good.
In but a few short dozen years, the humans advanced astronomically, almost like they could’ve always done so, and joined the intergalactic society.
And after joining it…the human race flourished.
The people of Earth have been friendly, even submissive when needed, and sturdy and completely unyielding in other circumstances.
This made it for them easy to make friends and hard to make enemies, especially since being new-joiners, they’ve been under the strict supervision and protection of the Alliance’s board.
Also, those from Earth loved to make gifts to those whom they’ve met for the first time, which was an unusual custom in the intergalactic society, and it was very warmly welcomed.
But…
Humans were humans, and they easily changed, yet never truly did so…
So customs and traditions from Earth started to spread…
One such custom, saying, was once uttered during a game on a space station, and that was the first piece that fell.
That was when the intergalactic society was introduced to…luck.
And that was what started its end.
Prior to this, the concept of luck wasn’t present, at least not amongst the hundreds of civilizations that made up the Alliance.
For better or worse, these civilizations were built on the ruins of an ancient empire that spanned across this entire quadrant of the universe they were in.
Thus, they all developed in similar ways, that’s how the Alliance had such a strong unity, and high speed of development.
But…
The ancient empire was an empire of facts, numbers and science at its peak.
Luck was long forgotten by its members, coincidences were long made obsolete by the highly sophisticated computers…
And that’s how these new civilizations developed as well.
Without luck existing as a concept.
And whilst their computers correctly estimated almost everything, there were impossible scenarios.
Random space storms, random implosions of stars, collapsing planets and many more…
These unexpected events spurred the Alliance to better their technology, better their calculations, but the concept of randomness, of luck, of coincidence never came up.
They simply never had it in their vocabulary.
That is…until now.
As the concept spread, and it spread faster than fire in a dry season, the Alliance simply collapsed upon itself.
There was a divide that formed.
Some started asking very unsettling questions.
What was the point of hard work, when you could randomly suffer a misfortunate event?
What was the point of developing new measures against the other galaxies, if they can simply get lucky, unearth ancient technology and wipe everyone out?
What was the point of maintaining order, when it won’t amount to anything, in front of the infinite possibilities, that now are unable to be estimated?
The other camp was thinking in the opposite direction.
If luck exists, coincidences do exist, and there are things that they can’t estimate, then they should be trying harder, trying new things, travelling more and so on…
Long story short, due to the debate, the Alliance lost more than half of its members, while the rest started to act more and more individualistically.
Earth gained the most out of it, as those who lost all hope, didn’t bother them, while those who gained new dreams, came to Earth for guidance, and advice.
But the Alliance wasn’t what it was before…
So the prophecy was right…
And the humans did it unintentionally…
Or so one might think, but who knows the truth, after all, Earth became the richest civilization of the Alliance after the split happened in but a few centuries…