Its natural for the plant material to dry from the outside in. Especially with thick buds, the outside will be crispy while inside is very moist and unsmokable. Just cut open a drying bud to confirm this.
Placing the buds in jars at this point serves to even out the moisture content as it is drawn into the drier tissue. When this happens it's time to take them out and dry the outsides again. Repeat until you have reached your desired moisture levels. The slower this happens, the better the buds become. This is curing.