Yes nobody would care that they lost to Liverpool if Chelsea win the Champions League, but they can't just put all their eggs into one basket. They're playing Bayern Munich AT Munich, and whether or not they think they can win, they still needed to try to make the Top 4 by beating Liverpool and Blackburn. They were always still a possibility, and if they beat Liverpool than they would've been the big winners out of the four teams fighting for 3rd and 4th spot.
Yes they would still need teams to slip up, but they wouldn't be the only ones. Man Utd are hoping Man City slip up, Tottenham are hoping we slip up, Newcastle are hoping both us and Tottenham slip up. Beating Liverpool would've meant Chelsea would still be in the running, but now they'll finish sixth and I bet they'll lose at Munich.
Di Matteo said when he was first appointed that he would need to WIN the FA Cup, WIN The Champions League AND get Chelsea into the Top 4 to even have a chance at keeping the job. Well he won the FA Cup, but he blew the chance for Top 4 and it'll only be saved IF Chelsea beat an awesome Bayern Munich team on their home ground. Won't happen.