It has 0 to do with "intelligence."
In fact, engineers are typically not of the highest IQ.
It has to do with why many people with high IQs have trouble with algebra.
It's often the kid with only an IQ of only 95-115 that has to write things down and learns methodical, precise approaches to get complete answers that become engineers.
That's the reality, and why we're pretty much fucked in the US now.