Is a person who did not pledge allegiance to a ruler who seized power through fraud and force, and died in that state—especially after this person was no longer a ruler—considered to have died a death of ignorance (jahiliyyah)?

A Muslim is not obliged to pledge allegiance unless people agree on an Imam who can fulfill the purpose of legitimate governance. The Imamate is established by the approval of the people of power (Ahl al-Shawka) over it. A man does not become an Imam until he is approved by the people of power, through whose obedience to him the purpose of the Imamate is achieved. So, if he is given a pledge of allegiance that grants him power and authority, he becomes an Imam. And whoever overcomes them by the sword until he becomes a Caliph and is called the Commander of the Faithful, it is permissible to pay charities (sadaqat) to him, whether he is righteous or wicked.

The meaning of the hadith "Whoever dies without an Imam dies a death of ignorance (Jahiliyyah)" is that it is not permissible to revolt against the ruler except in the case of clear disbelief (kufr bawwah), and it is obligatory upon the Ummah to appoint a leader who looks after its interests. However, if Muslims do not have a community or an Imam, then the Muslim should withdraw from all those factions, even if he has to bite onto the root of a tree until death overtakes him in that state, for fear of falling into evil.