Why was the first ocean waters so acidic?

According to Dr. Halevy, he has said that billions of years ago, "the early sun was dimmer, even though we don't have evidence for a much colder climate. We think that this is because the early atmosphere had more of the greenhouse gas CO2 than at present, and that as the sun got brighter, CO2 levels decreased". Hence in the primitive time, life and chemical cycles thrived while the ocean water was more acidic as compared to the present time.

The amount of carbon dioxide in the atmosphere rises and the oceans just absorb it, in the ocean, carbon dioxide reacts with seawater to form carbonic acid, that causes the acidity of seawater to increase.