In one theory, it's stated that because people focus too much on the lives of celebrities, they tend to think that they divorce a lot while their divorce rate could be similar to that of normal people.
Celebrities usually have so many fans. Some of those fans might be attractive while some others might be other celebrities. This can make them more likely to seek someone else especially if their marriage isn't going well.
Some celebrities date other celebrities to get more publicity or to do strategic career moves (See also why Kim Kardashian is so famous).
Celebrities usually have enough money to care for their children and to start a new family. This reduces one of the barriers of divorce.
The life style many celebrities have allows them to meet many attractive people. If one of them isn't that satisfied with their current marriage then breaking up and starting a new relationship might seem like a good idea (See how to get over someone).
The busy schedules of most celebrities can prevent them from spending enough time with their relationship partners and so bonding might not properly happen.
Actors can develop crushes on other actors they act with, especially in romantic roles. This can create some kind of temptation to start a new relationship.
According to one study, women who can support themselves tend to be more selective. If the woman doesn't find what she wants in a relationship then getting divorced might be an easy option for her, since she won't have to worry about money.
Some celebrities are egocentrics, while some others are narcissists. Both types of people can find it hard to think of others if their own happiness is compromised, which can lead to a higher divorce rate.
It's not uncommon for a celebrity to drop out of fame or to lose their edge. Because the drop is usually big it can create a lot of stress and tension that leads to divorce (See why 50 cent filed for bankruptcy).
According to one theory celebrity divorce is much easier because celebrities usually have enough money and fans to move on fast and find someone else quickly.