Complex sentence: However, they all disagreed with Roisin's firing, as they believed her performance had been exceptional, and that her business plan only needed tweaking; until her firing, she had been considered a favourite to win.
Split into simpler sentences: However, they all disagreed with Roisin's firing, as they believed her performance had been exceptional and that her business plan only needed tweaking. Until her firing, she had been considered a favourite to win.