The very moment flash was not included in the iPhone, Steve Jobs had a vested interest in seeing Flash fail. If Flash expands, user satisfaction with the iPhone goes down. If Flash fails completely, one of the strongest negative components of the iPhone disappears.
Why does he have a vested interest in making it fail? Could he not change his mind and allow Adobe onto the platform? It's not like he's never changed his mind in the past (the Intel vs PPC 'Megahurtz Myth' comes to mind).
I would argue that it was even sooner that that. The Steve has probably hated Flash for a long, long time.
Yes, this goes back to 1989 fight over fonts, and the 1993 fight about Display Postscript and the 1999 fight about Photoshop on Windows, and the 2007 withdrawal of 64-bit Carbon toolkit at the last minute.