not all cults are religious

On November 18, 1978, 909 men,women, and children died
after being forced to drink poisoned Flavor Aid.That grizzly image has since been immortalized as shorthand slang for single-minded cult-like thinking,They drank the Kool-aid.Today, there are thousands of cults around the world.It's important to note two things about them.First, not all cults are religious.Some are political,therapy-based,focused on self-improvement,or otherwise.
And on the flip side,not all new religions are what we're referring to as cults.So what exactly defines our modern understanding of cults,and why do people join them?