Yeah, none of that sounds concrete to me at all. It sounds like bullshit. The probably felt pressure to solve this because it gained so much attention, and they just came up with some BS story. Not finding anyone elses DNA or fingerprints doesn't mean that no one did it. There are so many more ways he could have killed himself if it were just for insurance reasons. He could have driven his car off a cliff, or into oncoming traffic.
And how sad if he did do this for the money. All that trouble and actually taking his own life, for nothing.