If he knew he was leaving why didn't he leave after the last game of the season ?
If he didn't fancy the offer that was on the table he could have walked weeks ago.
Why do you think he's waited so long ?
Why should he quit straight away? He has a contract of employment. He, like everybody else with a contract of employment, is entitled to seek out other opportunities whilst still under contract.
He waited because that was the best option for him.