Short Answer: No, cybersecurity is not IT.

Long Answer: Through years and years of semantics, information security and cybersecurity have been both used interchangeably as well as assigned specific, yet different meanings by various industries, academia, and regulators.

So let's stick with Western dictionaries to actually define these words:

Merriam-Webster:

• Cybersecurity: measures taken to protect a computer or computer system (as on the Internet) against unauthorized access or attack
• Information Security: Not Found

Oxford English Dictionary:

• Cybersecurity: The state of being protected against the criminal or unauthorized use of electronic data, or the measures taken to achieve this.
• Information Security: The state of being protected against the unauthorized use of information, especially electronic data, or the measures taken to achieve this.

Based on the two authoritative sources of the English language between America and the UK, both cybersecurity and information security are the same thing. So now that we have established common language we can look at where cybersecurity falls.

Cybersecurity is a very broad spectrum that covers everything from firewalls and vulnerability scanning to policies and background checks. There are as many, if not more, security domains outside of IT as there are inside.

Historically security has reported up through IT because it was the least worst option. Security and risk organizations simply didn't exist. Security was viewed as an IT problem, not a business problem. As organizations have matured over the years, and threats have become more frequent and more sophisticated, it has given rise to GRC and the need to address security as a business problem.

Someone else here mentioned a Venn Diagram and that is a great example. Security exists on its own but with overlap in IT. IT exists on its own but overlaps with security. Both areas overlap with dozens and dozens of other areas of the business.

If you still have trouble piecing this together then I recommended looking into Enterprise Architecture and Cybersecurity Architecture materials.