Why was Charles I unpopular?

Think over the factors at play in society and how Charles I's actions affected them - religion, for instance, had caused difficulty and violence for all the Tudor monarchs since Henry VIII, and this had only been tentatively settled by Elizabeth I and James I&VI, meaning that Charles' apparent actions in favour of Catholics would cause tension. The structure of the court, too, would reinforce this tension between Charles I and his subjects - the expulsion of the gentry, and the facade of decadence, did not promote popularity amongst subjects in the countryside. This was coupled with the fact that he did not make an effort to meet many subjects, and therefore did not contradict this reputation that he was building up. The personality factor is a big one, too - as well as being shy and antisocial, he was viewed as weak, too. So you can see just from these few points that Charles was building up an unpopular reputation that would cause tensions within society. If you look further into the factors at play in the years leading up to the Civil War, from the evidence that we have, you can see how quite easily he was able to become a highly unpopular monarch.