�Why Robbie Lawler is not fighting in Pride after his great debut with a KO knee against Joey Villasenor?

I had already mentioned this way behind a case one or two days, i talked about Vitor Belfort and now i asked about Robbie Lawler, why excellent fighters like Vitor or Lindland and now Lawler are not fighting in the big leagues, Lawler is an excellent artist of the knocked out, not for anything they call him "Ruthless". not even in the UFC Lawler fought again.