Players often believe they are in control of the relationship, and they generally walk away before they can be left. Some of them occasionally have a partner discover their games, and they can find they are being asked to leave before they are ready. Some of them may feel regret because they have lost a great partner, but they are unwilling to let that show. Rather than being happy, they are pretending happiness so they still feel in control.
Going out immediately when a partner has dumped them is often the response of a player who has been unmasked. They believe that it is easy to find someone else, but they are not necessarily picky in their choices. They just want to be with someone so they can look like they are fine with the situation, but that could be far from the truth. They could be emotionally devastated, but letting it show runs counter to their philosophy of relationships.
There are some players out there who are almost professionals in their lack of caring for a particular partner, but others are often those who chanced to get away with an affair once. They may have stumbled into it without thought, and the consequences are more than they imagined. Their devastation could be real, yet they know it is deserved. They would still rather look good to the world than admit they made a horrible mistake and lost the love of their life.
Few people are willing to put up with a player once discovered, and they would rather suffer a short period of unhappiness than a lifetime of grief. It may be difficult to watch a former partner happily dating someone new, but it is not worth the lack of trust and respect to stay with a player. Future happiness is the goal, and ignoring their happiness is the best way to achieve it.