Hi, I can't say for sure what happened, but if you planted them in full sun and rich, organic soil, they should have done well. Personally, I think it's best to buy plants rather than sets because I've had sets grow, set seed and die quickly. Onion plants, however, never seem to fail at producing a crop. Also, onions like a wet soil. They certainly require good drainage so muddy ground is not good, but they like moisture and an organic-rich soil.