Is a crack addict actually crazy?

There is only one thing that is of interest to a drug addict and that is where the next "drug fix" is coming from.
Many dont have enough money to buy each time so resort to crime to fund their habit.
When they get desperate enough that it becomes a matter of life or death (in their head) they will do anything it takes to get the next fix.
Hence the term "crack head" as actually the brain no longer functions likes a sensible person.

Crack head is often used to refer to someone on crack but commonly used for any drug addict.

Nothing you’ve said is strictly incorrect but it feels like an incredibly stereotypical description of addiction, just based of the way it’s portrayed in the media.

Addiction is a mental illness and sure, constant drug highjacks normal brain function so people develop beliefs not based in reality;
But just like any other illness, the way symptoms manifest vary massively, as does the severity. Anyone can struggle with a drug addiction, there are many ‘functional’ addicts that are capable of holding down a job, affording their habit and being a trustworthy friend and family member. Stigma causes a great deal of damage, the assumption that everyone with that illness is violent, has no mortal principles and participates in criminal behaviour makes people too afraid and ashamed to ask for help.It’s not a moral failing, It’s a coping mechanism, trauma response, consequence of other mental illnesses or consequence of poverty.

Unfortunataely my experience is nothing from the media but having someone close to me who has destroyed so many lives by their constant drug addiction for some 20 years now, we have all been victims of the abuse they deal out.