If he stayed with the Tigers he would not only boost the profile of the NBL in Australia, but the NBA here as well. Both are needed.
He knew what he was getting into going to play in China: a league with low quality of play, no defense and no NBA-out clause.
He can always chase a big pay day elsewhere in Europe or China later, even if he never sets foot in the NBA again. This was his one chance to play in the NBL.
Also, Portland are having immense troubles at the PG slot, with Felton posting career low numbers. Had he stuck it out in the NBL he'd likely be back there before the trade deadline, or at worst be fighting for the fourth playoff spot with Melbourne.
Instead he's stuck with no FIBA release from a crazy Chinese club who hates him.
Also, staying in the NBL would have boosted his profile immensely at home and opened up sponsorship opportunities here for him. I don't think many of you realise it, but no one in the general Aussie public has a clue who Patty Mills is.
Staying a little longer would have allowed him to grow his personal brand.