The parable of the sower comes to mind thinking about them and their choices.
"When any one heareth the word of the kingdom, andaunderstandeth not, then cometh the wicked and bcatcheth away that which was sown in his heart. This is he which received seed by the way side."
So the first is not really understanding to begin with.
"But he that received the seed into astony places, the same is he that heareth the word, and anon with joy receiveth it; Yet hath he not root in himself, but dureth for a while: for when atribulation or bpersecution ariseth because of the word, by and by che is offended.
Secondly, no root to what they believe, so when hard times come, or they see someone being a hypocrite or just not meeting their expectations they're out.
"He also that received seed among the thorns is he that heareth the word; and the care of this aworld, and thebdeceitfulness of criches, choke the word, and he becometh unfruitful." (riches could be knowledge, material wealth, status, partying, or any number of desirable things)
And third, temptations of the world, and living by the world's standards, being fearful of not knowing enough or being thought of as ignorant - slowly makes what you once understood seem less important...until that thing you seek is more important than anything else.
I hope that someday, they will return and reap the blessings and rewards of staying faithful and loyal to a cause far greater than anything this world has to offer.