Question: "Why did God take Enoch and Elijah to Heaven without them dying?"
Answer: Genesis 5:24 tells us, "Enoch walked with God; then he was no more, because God took him away." 2 Kings 2:11 tells us, "...suddenly a chariot of fire and horses of fire appeared and separated the two of them, and Elijah went up to heaven in a whirlwind." These two verses describe the only two occurrences in the Bible of people be taken to Heaven without having died. Enoch is described as a man who "walked with God for 300 years" (Genesis 5:23). Elijah was perhaps the most powerful of God's prophets in the Old Testament. There are also prophecies of Elijah's return (Malachi 4:5-6).
Why did God take Enoch and Elijah? The Bible does not specifically give us the answer. Some speculate that they were taken in preparation for a role in the end times, possibly as the two witnesses in Revelation chapter 11, verses 3-12. This is possible, but not explicitly taught in the Bible. It may be that God desired to save Enoch and Elijah from experiencing death due to their great faithfulness in serving and obeying Him. Whatever the case, God has His purpose...and it is not always for us to know or understand.