Johnson's financial situation is well documented. If anyone wants to understand the specifics about what happened between him and his parents you can give it a quick google search. But all people need to know is that he has filed for bankruptcy, and most of his income is now debt re-payment.
With this in mind, it seems pretty clear that this is financially motivated. That's not a slight against him, by the way. In fact, it's entirely understandable. Jack needs to make as much as possible on his next contract. And, as an upcoming UFA, he can already negotiate with the Jackets.
Knowing that (1) he needs money, and (2) he is free to negotiate with his current team, and (3) he has asked for a trade, it's safe to assume the negotiations are not going how he would like. He's probably not going to get paid what he wants on that team. If CBJ are not going to pay him a substantial amount on the next contract, and he needs the income, then he has no choice but to search for it elsewhere. I'm betting he would like to sign a contract before hitting UFA, as that is more security for him.
He wants to go somewhere that might pay him more. Hope he finds what he is looking for.