I think Brendan stepped aside to let Lulu take centre stage. She's absolutely amazing for a woman in her seventies. The wardrobe department did her no favours in their choice of dresses, and I don't think Brendan's choreography did her any favours at the beginning.
Perhaps she hasn't the stamina she had in earlier years, and that should be taken into consideration when considering the hours she put in.
I'm sad to see her go, and I'm sure she thanked him off camera. I hope we see her back on television very soon.