Why was earth 3D STS?

[Bosphorus1982]

I know we're headed into 4D STO but Ra's own planet Venus was a 3D STO planet.
My question  is why was Earth a 3D STS planet?
I think that's quite obvious in today's world that we still are until the harvest fully ends(time period given was something 100-800 years?)
Why is there the need for 3D STS planets at all? Is it because we're the fallen ones and unable to incarnate into any positive third density planet?
In my opinion this is the only reasonable explanation which is that we don't deserve any better. Like the fallen angels rebelling against god.
So before everything went wrong  humanity lived in a sort of etheric 3D STO state. Then humanity met the beings of negative polarity who tempted them and humanity fell. The veil was placed to accelerate spiritual evolution and now here we are in 3D STS with the veil.
This obviously didn't happen to Ra's social memory complex. Is it because they had the veil from the very beginning ? From 2nd density to late-stage 3rd density?
If that is all the case why was the veil placed after humanity made the choice?
It would have been better if it was placed before. In my opinion this would have allowed us to progress quicker and probably decrease the chance of turning into STS. Does that imply that Ra's society in third density made the choice to continue into 3D STO whereas humanity simply chose the "wrong option"?

Simply put: Are we(humanity) to blame for the mess we're in?

Sorry a lot of questions but I'm really trying to understand this.

It's not mostly human race who is responsible for the world we live in. There has been conditions that have been beyond our control and will. Therefore it is mostly the Orion 4D STS who made all the negativity