Why two questions?
The only thing that I can think of is that it's a rite of passage, like marriage, that must be entered into with the consent of the individual.
At a wedding ceremony both the bride and the groom give their consent to be married to each other.
At a JW baptism, the first question has to relate to the candidate's meeting the conditions for baptism:
February 15, 1964 Watchtower, pg 127:
1 Have you repented of sin with such restitution as you are able, and are you trusting in the merit of Christ's sacrifice for the forgiveness of your sins and the basis of your justification?
May 1, 1973 Watchtower, pg 280:
1 Have you repented of your sins and turned around, recognizing yourself before Jehovah God as a condemned sinner who needs salvation, and have you acknowledged to him that this salvation precedes from him, the Father, through his Son Jesus Christ?
June 1, 1985 Watchtower, p30:
1 On the basis of the sacrifice of Jesus Christ, have you repented of your sins and dedicated yourself to Jehovah to do his will?
The second question is a statement of the terms and conditions that are expected of the candidate after their baptism:
February 15, 1964 Watchtower, pg 127:
2 Have you made a full consecration of yourself with all the powers that you possess talent, money, time, influence all to the Lord, to be used faithfully in His service, even unto death?"
May 1, 1973 Watchtower, pg 280:
2 On the basis of this faith in God and in his provision for salvation, have you dedicated yourself unreservedly to God to do his will henceforth as he reveals it to you through Jesus Christ and through the Bible under the enlightening power of the holy spirit?
June 1, 1985 Watchtower, p30:
2 Do you understand that your dedication and baptism identify you as one of Jehovah's Witnesses in association with God's spirit-directed organization?
The order in which the questions are asked is important too. The first question is more innocuous, more germaine in its intent, and more likely for the candidate to respond to in an affirmative manner. Once they've put one foot over the thresh hold, it's difficult - in a public situation - to step it back in protest to the second question that ultimately involves putting your conscience on the back burner to do the will of the "spirit-directed organization".