4th division creating problem is a myth, plenty of La Liga clubs has their reserve teams playing their and don't have a problem keeping their talents.
Virgili is a player who joined Barca a year ago, and barely has any loyalty to the club. He saw he has no chance to play with first team while other clubs offering him place in La Liga. It won't matter if it is 3rd division or 4th, it is still not comparable to La Liga.
Same with Kospo, he came from Swiss 2 years ago, realized he isn't making it to first team and moved on.
If 4th division is the reason, then it is actually something we should welcome, we are finally more ruthless with our youth players and moving on faster rather than hoarding talents until it is too late to get something for them.