The Bible des not say, “God chose Moses because”... At Hebrews chapter 11, we do see why Moses chose to serve God. For there it says: 24 "By faith Moses, when grown up, refused to be called the son of the daughter of Phar´aoh, 25 choosing to be ill-treated with the people of God rather than to have the temporary enjoyment of sin, 26 because he esteemed the reproach of the Christ as riches greater than the treasures of Egypt; for he looked intently toward the payment of the reward. 27 By faith he left Egypt, but not fearing the anger of the king, for he continued steadfast as seeing the One who is invisible.” It is important to remember that it was God’s purpose to deliver the Hebrews by the hand of Moses. When Moses was 40 years old, God’s due time had not yet arrived; neither was Moses yet qualified to serve over God’s people. He had to undergo another 40 years of training. The qualities of patience, meekness, humility, long-suffering, mildness of temper, self-control, and learning to wait on Jehovah needed to be developed in him to a higher degree, in order for him to be the fitting one to lead God’s people. He had to be groomed and prepared to endure the discouragements, disappointments, and hardships he would encounter, and to handle with loving-kindness, calmness, and strength the multitude of problems a great nation would present. He possessed much learning, and his training as a member of Pharaoh’s household had doubtless given him dignity, confidence, and poise and had accentuated his ability to organize and command. But the lowly occupation of shepherding in Midian provided the training needed to develop fine qualities that would be even more important for the task ahead of him. In reading through the Bible, you can sense that God does not give anyone such a large task before they have been trained for it. Consider that David also underwent rigorous training, even after being anointed by Samuel, and Jesus Christ was tried, tested, and proved, to be perfected as King and High Priest forever. “He [Christ] learned obedience from the things he suffered; and after he had been made perfect he became responsible for everlasting salvation to all those obeying him.”—Heb 5:8, 9. Sources: The scriptures cited and the publication, "Insight on the Scriptures", Volume II page 434,1988 Watchtower Bible and Tract Society.

We do not know why God sought Moses, or why He seeks any of us. Presumably, He sees something that we do not see. The amazing thing is, when He enters the life of a person, it revolutionises them and, when you look back at their life, you say "Wow!Look at all the strengths he/she had, that no one realised at the beginning."