Well it didn't always happen, but it has happened where a ruler would retire from his rule for reasons other than mental incapacity and if the next ruler died without a clear heir, or the next heir wasn't old enough, would take over as the ruler again or regent. In CK1 the only way to retire was to do so the permanent way.
Even if they didn't they still would often try to influence things. This type of dynamic where the current ruler is trying to rule the land while the previous ruler still retains the a lot of the status could lead to some interesting results.
Even if they didn't they still would often try to influence things. This type of dynamic where the current ruler is trying to rule the land while the previous ruler still retains the a lot of the status could lead to some interesting results.