There are at least two categories when discussing whether Chelsea is expected to win the Champions League or not. First, it's the fans, and it shows their attitude towards the club they love, and it's natural to expect Chelsea to win. Second, it's the management and the players themselves, as winning the title would benefit them financially.
Some people immediately said Chelsea weren't in the right condition to compete for the title, especially considering the results of their opening Premier League matches. But sometimes we forget how Chelsea were able to win the Champions League despite their inconsistent performance in the Premier League when they were coached by Di Matteo, although sometimes it is not the same now.
The problem is the fact that they won CWC so now everyone expects so much from them. But in reality, just because they won the CWC doesn't mean they are going to be great. Things change a lot, like how they won UCL once, beating City and be the best, like they were not even that great on premier league, and yet won the UCL, so sometimes things are a bit different.
So this high expectations, stemming from beating PSG, cold put pressure on them to try to win the UCL, or maybe premier league at least, like win "something", no matter what it is. But it may not come to frustration because they are not doing that crazy well, it has to be something that will depend a lot on a lot of things, so we need to make sure it's all fine.