Kings used to be very scared. Someone always wanted to take their throne or get them out of the way by killing them. Even today it is not easy to be a monarch. Modern monarchies may not have much or little political power, but the dangers remain. That’s why powerful royal families spend a large chunk of their annual budget on security.
Queen Elizabeth is one of the most powerful personalities and that is why from her coronation onwards she is considered a target with many times violent attempts have been made against her. In fact, there was a time when someone shot at her during a trip to New Zealand. Luckily for her, she failed with the police trying to “cover it up” to avoid disapproval.