“The survival of DNA will always be a random process”
Only partly true. For successful horndogs like this monarch, it’s not random as to the next generation. If he has 200 sons, subsequent randomness will favor his genes over a randomly selected guy in his generation.
Also, if his success and abilities are partly inherited by those sons, or passed on by the fact they are a king’s kid, his sons would also have a reproductive advantage for their, and therefore his, genes.
And, he may have just had good genes. Smarter, stronger etc. Or just really good looking. So their survival would be favored in a natural selection process.
For successful horndogs like this monarch, it’s not random as to the next generation.The problem is, "this monarch" isn't actually known to have existed, making your statement a tautology. If a tomb had been found, containing the remains of someone (even an unknown) who was buried in something reasonably construed as a royal fashion, and his DNA was still in good enough shape to test, AND that turned out to be the DNA they're talking about, that's just fine.