Someone I know was absolutely desperate and prayed for the first time in years. Several days later an ex-neighbour rang her doorbell peddling the lies, which she bought as a sign from God. She worked on her husband who was out of work and on medication for depression.
Desperation, coupled with a tendency to trust (honest trustworthy people are the easiest victims because they believe others are trustworthy too) and a lack of knowledge of scriptures or Christianity are a recipe for potential conversion. Anyone with a solid grounding in Scriptures, especially the New Testament could not fall for this.