Because if you are selfish and ill-mannered, then your wisdom is earthly. In this way, your wisdom is of no use, because real wisdom does not have jealousy, heartlessness and selfishness. James describes in his words that jealousy and remoteness from God creates wickedness. He says, that you want to become wise, but you can not, because you ask wrongly. You ask for spreading selfishness and wickedness because you ask God only for your own.
Second reading is about the desire of wisdom.
It also creates the God's wisdom and world's wisdom. God's wisdom has generosity and prosperity but world's wisdom has meanness, misery, poverty and destruction. The gospel of Mark tells us two main ideas. After this we can say that a similarity exists between Jesus and faithful people and Jesus' wisdom and human wisdom. The above verse presents the main idea of greatness in wisdom.