Root rot

Is root rot when the dirt gets moldy? I just replanted one from a smart pot into the ground. The dirt in places was mushy grey and no root growth. Just did the same to one In a plastic pot. Is it the patio plus dirt? It looked kinda funky when I got it but thought nothing of it

I don't know about potted plants, but my plant had mushy grey mold in the dirt around the stem due to organic fertilizer(banana and banana peel's) high on K and P, plowing the dirt might help.