To train a model, it requires a lot and a lot of parallel computing, this means that each operation is very simple and disjoint from one another but the shear volume of computation needed is too expensive for the current hardware. Quantum computer can use superposition to concurrently compute every operations at the same time without needing any extra cores. This is extremely valueable as training will now only takes seconds as opposed to days and the cost will be around 10$ as opposed to thousands of dollars.

This is from my own understanding so it might be incorrect to some extent.