I think Cohen was trading a short stretch in ClubFed to avoid a long stretch in NY state prison. Trump could pardon him for federal tax evasion, but not state tax evasion.
This is why Cohen is “composing” in his plea arrangement. This strongly implies he literally had nothing else to offer. Probably why he hired Lanny, as well. He needed a heavy lifter to help him sell it to the deep state in NY.
Good observation. If he had problems paying Federal taxes, it seems logical he would have the same problem paying NY city and sate taxes..