Payet completed his £25million move to Marseille yesterday after going on striker at West Ham.
The France international refused to play for the Hammers following his last appearance as a substitute in their 5-0 FA Cup thrashing to Manchester City on January 6.
And West Ham chief Sullivan, who blasted Payet in a statement confirming the transfer, has revealed more about the 29-year-old’s behaviour over the last month.
Dimitri Payet isolated himself during his last days at West Ham
West Ham rebel Dimitri Payet continues training with the reserves
Tue, January 24, 2017
West Ham want-away Dimitri Payet has been snapped training with the reserves again
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Dimitri Payet was snapped training with the West Ham reserves today
“I think for the last six or eight weeks, he's not been talking to anybody in the squad,” Sullivan told BBC Radio 5Live.
“He's gone to the corner of a room for his meals and isolated himself from everybody. Before that, he was bubbly and happy, shakes everyone's hand before the match.
“Either it was a tactic or something in his head had changed. The team wanted him out. The manager, with the greatest reluctance, wanted him out. And as much as we didn't want him out, you can't go against the consensus of the team and manager.”
Dimitri Payet joined Marseille from West Ham for £25m
Payet was widely criticised for how he forced through his West Ham exit, but Sullivan revealed Marseille were also tricky customers in negotiations.
“(Marseille) were very difficult to deal with,” the 67-year-old added.
“They're lucky we accepted the £25m. I think he's worth more than that. The player's surrendered his January wages, which is another £400,000 or £500,000 so you get that there.
“There's a little bit of dignity we got with that. That was a deal breaker to us. Our attitude was you've refused to play – why should you get paid?”