I partially agree with your sentiment.
However, and perhaps it’s just semantics, I disagree that “secure” individuals are more likely to be “terrible” than insecure people.
I would argue that your definition of a “secure individual” as “bold and brash” is far more indicative of an insecure person attempting to receive external validation from their peers or superiors through false displays of power.
If we think of self-esteem on a continuum, arrogance lands on one extreme end and meekness lands on the other. The “insecure” people you reference above are not fully insecure (i.e., profoundly meek), for if they were, they would never be able to achieve the greatness you allude to in your article. Achieving greatness requires risk taking, and at least a shred of belief in yourself. Not for the meek of heart.
Insecure individuals will accomplish less genuine and impactful long-term achievements since they are more prone to simply bend to the whims of their boss/public wishes/other external factors. With a short range view, these people may in fact seem “great” as they fulfill all of your immediate wishes. However, from a long-term perspective, these people will never be “world changers”, because they lack the unshakeable “security” to follow through on something that others might actually disagree with.