Unless root damage occurred from the landscaping project, the symptoms of wilting collapse of half the plant in the second photo suggests that either significant root stress occurred or perhaps an opportunistic infection took hold. Root rot is one possibility (Vitex require good drainage and don't handle soil compaction with wet conditions well, if over-watered) but a wilt type of disease is another, though we have limited information from reference materials as to which specific pathogens they are vulnerable to. (Verticillium Wilt is common among other species, for example, but little mention is made of Vitex.) Not all of those pathogens will create notably darkened or mushy roots. You can examine the inside of split-apart wood on the wilted branches to look for indications of darker staining, which would suggest an above-ground infection of the vascular system (the tissues transporting the moisture and nutrients around the plant). Such infections usually arise after environmental stress first weakens the plant, and they are not curable.

The condition of the exhumed root ball show that it did not establish well at all because the root ball is still in the shape of the pot. Do you know if the roots were loosened well upon removal from the pot during planting? If not, that would explain its condition and struggles establishing; if it was, perhaps more was needed as the roots didn't grow far afterwards for some reason. Watering several times a week sounds a bit excessive, but it's hard to say for certain because it depends on how much water was being applied (and how much soaked in) compared to how quickly the soil was drying out. Vitex have above-average drought tolerance and aren't too picky about soil type, but do need good drainage and prefer to not get too dry between waterings while also not staying damp. Feeling the soil about six inches deep is a good way to monitor for watering needs; if damp when checked, watering can wait; if it's becoming somewhat dry instead at that depth, then watering would probably be beneficial.

If this location is still receiving full sun (6-8 or more hours of direct light in summer) then you can try planting another Vitex if you would like to try again, since they do not grow or flower as well in partial shade. (They are non-native but so far have not behaved invasively in Maryland...at least, not this species of Vitex.)

Miri