First off let me split the hair between a conspiracy and a conspiracy theory. Clearly people do conspire and that process is a conspiracy. People conspire to smuggled drugs, contraband, and people across boarders, they conspired to evade their taxation debt, they conspire to conceal evidence of guilt and all manner of things. The real difference is the scale by which real world conspiracies operate and the vast global coordination required for many popular conspiracy theories. A few conspiracy theories that serve as example to me of this deluded impossible thinking:

AIDS was a created disease to eliminate certain racial groups.

The Moon landing was faked.

The US Government has possession of alien technology.

Marxists, after their ideology was discredited, disguised it as post-modernism to infiltrate it into popular culture.

Vaccines cause Autism or mental defects.

International ‘globalist’ (and we all know what that’s code for) control world events. (That one gets tied to Marxists as well.)

9/11 was an act of the US Government.

I admonish everyone to demand proof, not conjecture, not assumption, but evidence before believing vast glob spanning causes for events.