How we change what others think, feel, believe and do
Conspiracy theories are often based around individuals and organizations who are members of the conspiracy. These can range from powerful individuals to international cabals.
Individuals have purpose, and when they gain sufficient power, for example through acquiring money, influence and so on, then they may use that power for questionable personal gain.
It is easy when you have power to see yourself above the law and perhaps seek to control those who create and police laws, whether by bribery, blackmail or other means of influence.
Newspaper and media moguls have been accused of cover-ups as they control whole populations through carefully filtered information while they indulge themselves and continue to corrupt the system for their private purpose.
Companies are generally profit-driven. Their primary purpose is to return money to their shareholders. They may hence engage in unethical, immoral and illegal activities, such as callous use of people and dumping toxic waste rather than having it (expensively) processed.
It is arguable that many of the world's problems and social problems are caused by the profit-motive and the capitalist system that legitimizes this. Company actions are hence always suspect. Even if they have social and environmental policies, they have to make a profit to survive. The nice policies may in fact just be a cover-up as the profit motive comes both first and last.
Governments naturally want the populations in their countries to behave. They hence want to control what people know and what they think. In this, they may make significant use of propaganda, with control of the media through law and influence.
A clever illusion is that of freedom. Governments tell you that this is a land of freedom, while curtailing that freedom in all kinds of ways.
Governments, industries and even social charities set up agencies that may acquire their own and corrupted purpose, for example as they take their charter as being above laws and seek to meet their goals by any means.
Government agencies, especially those interested in security, may act like this as they (quite reasonably, of course) argue that security is so important, they must take all measures to ensure this. They may well view politicians as constrained by worries about tenure and criticism, and so 'do their dirty work for them'. Politicians may collude with this by not asking too many questions or looking too closely at what is really going on.
Organizations may also exist that have their own purpose, such as for political, religious, criminal or other ends. There is both attractiveness and scariness in the notion of organizations that answer to nobody, perhaps as seen in 'world domination' organizations are popular in thriller movies.
The world is a small place these days, and those who hold power tend to meet and seek ways of sustaining that power.
There are known groups of powerful people who meet in secret, and it is a small step to assume that a topics include power, control, money and how to sustain what they have and gather even more. Of course there is horse-trading in such as territories, backing and so on.
When powerful groups are proven to exist, and especially if they meet in secrecy, it is easy to extend this knowledge into proof of their actions as being corrupt.
Paradoxically, groups which suggest that conspiracy theories exist can themselves act like conspiracy organizations themselves, with secret groups and purposes. While this is not always true, it can be used as means of discrediting as any party in the conflict may accuse others of things where they are not necessarily guilty.