"They". Maybe "they" have it backwards. Fracking led to a boom in oil supplies, causing oil prices to drop. Many folks think of oil in terms of gasoline and diesel. However, thousands of products are made from oil. A few are plastics, fertilizers, animal feed, lubricants, makeups, asphalt for roads, roofing materials, paints, etc. A drop in oil prices drops the cost of ingredients in products, leading to a strengthening of profits and employment, and the drop in fuel prices eases transportation costs. The dollar is still losing value, as seen by rises in food and other costs. But that is temporarily offset by lowered oil prices for reasons I stated.
Actually, since summer, there is little question the dollar has gotten stronger.