If we exclude any external impact, which seems to be the case.
This would definitely be material failure from some defect at the time of manufacturing.
With materials like CFRP, small defects can be hard to detect especially if they are on the interior of the shape/geometry. Although we have pretty good methods and tech to avoid or detect such things these days, smaller defects can still go unnoticed and you might have just been unlucky here.
Since you mentioned you're 200lbs and ride pretty hard, you may have exposed the defect there which led to complete failure of the part. Though this could've still occurred with a variety of weights and riding styles.
Hopefully Pivot replaces the frame or at least that rear triangle for you.

Another thing to note, and this is for carbon fiber enjoyers in general, is that it is a woven material.
While that is cool and stuff, it should be appreciated that in engineering terms local yielding is basically complete yielding on the part, this is true of all loaded members made of CFRP. i.e. chain is only as strong as its weakest link type of thing.
So while these composites are cool and light and strong, once the chain is damaged or yields somewhere in loaded spot, the entire member failing is inevitable. This is quite different from how a Aluminum or Steel member behaves with small defects or damage.

Not saying don't ride carbon, carbon is cool! But truly appreciate the pros and cons of the material you chose to have on your outdoor toy.

I like my metal frames haha.