Have you ever worked a trades job? It takes "smarts" to be a good HVAC technician...it involves knowing and understanding practical thermodynamics, electricity, and mechanics.

Due to the evolving nature of the equipment that mechanical and electrical technicians work on, they now have to know how the equipment works, how its networked, and how to troubleshoot any problem involving the equipment. It isn't uncommon, at least in the industry I work in, to find technicians that have extensive knowledge of electronics, electrical/mechanical equipment, and even have their CCNA and good networking/system administration knowledge.