Psychological manipulation.
When I was on my mission I was often told to look for and focus on people going through a transition. Recently married. Recently had children. Recent death in the family. Loss of job. Etc..
It's marketing. The LDS church uses the very same techniques as those first formulated by
Edward Bernays during the mid 20th century (see
Century of the self).
After returning from my mission I went into direct sales and then marketing. The techniques I used on my mission worked well in both. Some of the same techniques are used by magicians and politicians.
Humans don't make purely rational decisions (see
Spock Fallacy). That is one of the the biggest misconceptions about human psychology and human behavior that there is. If you want to sell beer you don't point out that it makes you drunk. You sell an idea, a concept consisting of mostly illusions of youth, partying, happiness and or status and prestige. If you want to sell Mormonism you use love of family, fear of death, desire for community, desire for stability and convention. You use black and white thinking, purity vs evil. Most important you love. In the Mormon Church this is called
fellow-shipping or friend-shipping. In many cults it's often called
love bombing.