I think Ealing would have been promoted but they don't have the requisite ground and facilities to be a Premiership Rugby club.
For Tizzano, presumably it's better for his rugby to go somewhere he'll play regularly than be second or third choice at a Premiership club (if that opportunity was available to him).
He's good but you also wouldn't expect him to be recruited to be a first choice 7 for a team in the Premiership. He currently can't crack a Super Rugby matchday 23. He did very well last year in a team that lost every game.