They don’t necessarily follow one-another
You think they’d follow each other. But often they don’t. Armchair quarterbacks are high confidence, low competence. Imposter Syndrome describes high competence low confidence.
A lack of competence due to a lack of exposure (or simply the Mere Exposure Effect) will sometimes result in falsely high confidence. This is what the Duning-Kruger Effect is all about.
Confidence can be earned through exposure, perhaps through the use of drilling and Deliberate Practice. These things work because Raising the Floor is as Valid as Raising the Ceiling.