Running or walking technique is highly dependent on your core hip and pelvic control. I am yet to see a person with plantar fasciitis that I would say has good ‘form’ or technique.
This form/technique can transfer forces further down the chain requiring your knees and feet to work harder to control this additional stress.
When you become injured it is usually after your body has compensated to the point where things are no longer able to cope and something gives way. I call the plantar fascia the pop off valve as it seems to often be the thing that gives way in the end.
Orthotics and footwear are certainly important in assisting recovery at a foot level. However being aware of your core, hip flexor, gluteus medius and gluteus maximus function is just as if not more important. For example with ITB friction syndrome (runners knee) the signle most effectively proven treatment is strengthening the gluteus medius at the hip level. This reduces forces at the tensor fascia lata and improves gluteus maximus function, therefore reducing the load on the ITB.