He'd already gone off the boil for Liverpool well before they sold him - and they built the team around him and his strengths.
He still scored 9 in 23 games before the January window! I think Liverpool handled him very poorly in terms of rushing him back from injuries. The second he was able to run, they put him in the team, i personally dont think he was ever 100% fit in his last 6 months at Liverpool.
Like you say, they built a team around him and look what he did...65 in 102 league games. As i say, Chelsea's tactics dont suit his style of play. Stick him in the Arsenal team where they play fast attacking football and he would score goals. Like when he was at Liverpool, Gerrard would pick the ball up on the half way line and he was immediatly looking for the run of Torres...8/9 times out of 10 he would find it and look what happened.
He plays on the shoulder of the last defender, Chelsea dont look to release players early, they tend to build up play slowly working their way towards the edge of the box. Instead of playing 2 or 3 passes and slipping the ball through, they're happy to keep possession for 2 or 3 minutes.