Taking out large insurance policies has been a common motive for murder. It is reasonable to assume that one would become a suspect after a death if such a policy had been taken out and/or upped. Even if they are not the direct beneficiary. But murderers are not reasonable.
And the fact that a murderer, after the killing, fails to attempt to collect, does not erase motive. Many murderers, after the act itself, realize it may not have gone the way they had hoped and that the focus is too intensely on them. So, they likely change their planned course of conduct.
Did casey anthony, scott peterson, the coward who killed susan powell, etc., believe the heat would be so high? Inexplicably, even when smart enough to hide tons of evidence, murderers are often dumb enough not to anticipate the reaction the murder will cause. Somehow, they imagine themselves happily living out their lives after an initial, quick investigation and a sad, unsolved case involving a loved one.
BTW, I read the first post on this thread of yours in which you state that there isn't absolute proof that Jason Young did this. Absolute proof is not necessary for a conviction. And it is this belief that has contorted the meaning of reasonable doubt.
I don't know if there is reasonable doubt in this case, having not watched either trial, but there certainly seems to be proof. And in most cases that go to trial, the proof is not close to absolute.