Praise be to Allah, and peace and blessings be upon the Messenger of Allah. To proceed:
Whoever is killed unjustly among the Muslims receives the reward of martyrdom in the Hereafter. However, in the case of those who were killed here, two matters came together:
They were killed unjustly, because merely intending to commit a sin and wanting to do it does not make it permissible to kill a person. No one is permitted to take retribution against them by himself. Rather, they should be prevented from committing the sin through lawful and legitimate means.
They intended to use their land for something prohibited. Therefore, they should not be enabled to use it in this manner; rather, they should be prevented from doing so through the prescribed legal and religious means.
Accordingly, the ruling concerning them in this world is a matter for the court and the competent religious authority. As for their judgment in the Hereafter, that is with Allah تعالى. It is hoped that Allah will forgive what they intended because of what befell them when they were killed unjustly. The prescribed course is to pray for their forgiveness and mercy.
As for the killer, it is not permissible for him to kill them because of this sin, and he must bear the consequences and legal rulings resulting from his killing them.
In conclusion: Wanting to grow drugs is a sin, but it does not make it permissible to kill those who intend to do so. Those who are killed unjustly may be hoped to receive the reward of martyrdom. However, it is not permissible to definitively assert that they are saved from the punishment of the grave or to determine their condition in the Hereafter without evidence. Their affair is with Allah.
As a clarification regarding the expression mentioned in the question: it is not correct to say “the decrees willed it” or “the fates willed it”, because will belongs to Allah تعالى. The more accurate expressions are: “Allah decreed that” or “Allah willed that.”
And Allah knows best.