Actually, I think it's pretty easy to imagine. The first thing he wanted to do was get the bodies away from the scene of the crime. That's his first task. Why did he "go back" and write that check. Why did he write any of these checks. I'm not sure that we can know the motive behind every check, but I would think that he may, in the rush of things, wanted some money. A check. ASAP, before anyone knew the family was dead. He was there anyway, and wanted to get it done before having to deal with the bodies. So, he gets the bodies in the truck, moves it away from the house, goes back on foot and enters from behind the house, unseen, and writes a check.
No one will ever have all the aspects of this case down as fact, but I'm still confident, after hearing what we have from the state and the defense, that Chase is guilty. It's a whole picture.