Islam informs people, that the reason for human existence, in this world, is the test - on the road to heaven, or hell.
The most difficult test-questions occur in times of fitne. Any fitne is an acid-test of your spirit. It is the chaotical times, when lack of information may make planning difficult, or impossible, and/or where preferring the good may cost highly. It is a context of provocation(s), confusion, turmoil. Many weaker spirits may lose the test.
The main sources, or types, of the evil fitne may be
Any (evil) fitne may involve many evil agencies which invoke it, e.g: the satan, the witch-beings, the tyrannical/corrupt local states, empire/colonnialist powers, the antichrist, etc.
The lack of faith, is promoted by the satan(s), and by some of the eager faithless. Although, some of the unfaithful may establish their own mores, most may not stay at any limit, unless punishable by this-worldly means. This is the widely-understood answer to the question why lack-of-faith is problematic. In general, the lack of faith, is the eternal loss, the worst thing in existence, any way. It sends to hell, and it messes with the psychologies of many, even while in this world, yet. (Remedy: Islam.)
In a context of chaos, and/or in a tyrannical-and/or-corrupt establishment, the good-fitne is to restrain our acts, filtering our plans, through what Allah orders, and avoid what Allah forbids. We may also keep out of tyrannical-and/or-corrupt establishments, (minimizing, or altogether avoiding any contacts with them), not to participate in what they do.
On the page about the armageddon, I have interpreted a hadith of our prophet (s.a.s.), about white-fitne vs. black-fitne.
When the things were structured the wrong way, Allah may work His own ways.
When Allah revealed messages to the prophets, or revived them through other sincere people, in many cases, those were opposed by the towns-people, the establishment. Many of the prophets were killed, and others had to run away - at least, temporarily.
At times, instead of a total extermination of tribes, or leaving all punishment to hell, Allah renders His own craft, to warn the people, and to fight against the evil crafty nets. In Quran, it is written: "They build a trap/trick. We (Allah, Himself) build a trap/trick." At the end, it is fair that Allah wins, with whatever forces, and plans He owns, and the right is established. He may mobilize any of the, ordinary humans, angels, (shifts within the probability-ranges of) the reserved-forces in subatomic physics, etc. He already owns the universe, and not shy to "leave traces," either. History is full of examples of divine interference, the immanent justice.
A vesvese is an urge, feelings, or thoughts, the obsessions and/or compulsions. There may be several sources of it, and even patented technologies to manipulate people's minds.
A vesvese is a single-person phenomenon. But if it victimizes multiple people at once, either by manipulating multiple minds, or by urging any of the victims to hurt the others, than it is the satanical (evil) fitne - whether invoked by the satan, or by some witch-being.
Fitne is not necessarily internal. As a result, we may refer to an overlap of the ranges of vesvese and fitne. e.g: So often, even without anything about mind-control, the "deep state" agent-provocators, and even political parties, and sports teams, may be classified as fitne, especially when it leads to lethal conflicts, and/or tyrannizing (chrushing rights) through guns/military.
e.g: A scenario played by an evil manipulator, on multiple victims, to urge each of them to hurt each other, is such a provocation. The satan does it. The imperial powers do it, too - through their divide-and-conqueor motto.
A so-called agent-provocator, if not a cold-calculator, is probably an extreme-jealous, and possibly (also) a chauvinist of some group, who feels utterly against both of those sides, he/she is provoking against each other.
The good muslim acts good, by the standards of Islam, and expects the rest of it, from Allah. This is there. Humans cannot crave full control of the world. It would be only foolish-control, when for example, most computer software contain "bugs." We trust in Allah, the God.
In particular, it is fitne, when some evil urges (vesvese) the targeted (victim) persons, to bump them against each other. Islam warns people about the evil provocations of the satan, the antichrist (ed-deccal), etc.
Islam is our guide for eternity. We must filter our thoughts, and our plans, with what Islam orders. When we do it, we receive this-worldly gifts, too. e.g: Islam forbids escalation in retaliation. We must punish the criminal, with whatever is the right punishment about it, and we cannot "extend punishment" to hurt innocent people who were not related to the crime - even if a relative of the criminal. With this, we avoid a lot of (unnecessary) punishment, and thereby, probably avoid (unnecessary) troubles, either.
In a context of provocations, if people neglect the orders of Allah, the atrocities may be mutually-escalated, all at the same time, when both sides believe the other side must suffer even more pain.
The antichrist is also to do it. Beware.
Even our own needs and relationships may pave paths through the chaotical - in both the risk, and the relief senses of the sentence.
a multi-sided vesvese.