sometimes not a case of weak/strong though.
to pick one example
If you have a medially deviated subtalar joint axis, then it ‘could’ lead you to ‘over’ pronate (some pronation being entirely normal) and in some cases overpronation can elongate the points between the insertion/origin of the pf and therefore strain the plantar fascia leading to small microtrauma (generally around the heel) and hence the inflammatory condition pf arises, AFAIK no amount of ‘foot strengthening excercises’ on the foot’s internal musculature is going to sort that out, and correction of the subtalar joint axis path with an orthotic to bring the foot into a more rectus position can bring relief from this problem (and other associated alignment issues).
orthotic therapy has its place, for jcl’s info the days of whacking a massive lump under the arch are over, most orthotics now correct alignment issues by altering the path of the stj axis from wedging under the heel.