There's not point in blaming the club, Mendes, Mourinho. There are so many people from both sides in negotiations anyone could have let the secret out. Hands for the deal will have been shaken when BBC, and others first broke the news soon after he was sacked at Chelsea. LvG must have known many Months ago his time was up having been given assurances of his job until the end of season. This is the reason he was so confident he would not be sacked in January when questioned by journalists.
Even Lou Macari knew there will be news after the game having confirmed this to my son. Anyway, The club keeping quiet, extending season ticket renewal deadline were all indicators. Tickets sales have been slow for the season ahead. This news will now give a massive boost to sales.