Not everyone in Crusader Kings 3 wants to see your leader's point of view or is willing to help you with your political agenda. Because some of these individuals are your vassals, you cannot force them to see your point of view. It makes you a tyrant, and no one will follow you if you hurt them or make their life miserable. However, to encourage them, you can use a weak hook.
A weak hook can be a little secret or a favor someone owes your ruler when you do something for them. For example, after you capture a vassal that your ruler imprisons after catching a crime, there is an option to free them by asking for a favor. Alternatively, your rule might release them for a ransom, but a weak hook might come into play more than change.
You can choose to use this weak hook in different ways. Whoever you have this hook to might have a vote in an election that your heir needs to win to earn your title or kingdom. When you use the weak hook, you force them to vote the same as you for a specific time. You can also use it to force them to convert to your faith, relinquish a title, force them to join your court, imprison them, or join a plan you want to complete. These are extremely useful to obtain.
Imprisoning someone and giving them freedom isn't the only way to get a weak hook. Some random encounters happen with other leaders that may allow you to acquire one, such as at parties or working with them to continue their agendas. A weak hook doesn't last forever. It expires, and once you use it, you must win another against that individual. They don't refresh and don't come back.
Your ruler may also have weak brackets placed on it by others. Make sure you don't get stuck politically in owing someone a favor. You probably won't like what they ask of you.