The British were considered a super powerful army back then. They were organized, had more supplies, and had more skills and experience. The colonists on the other hand were just a bunch of men from towns with guns.
Sea explorations were made by many countries centuries ago. These were headed by the European countries long back. The impulses or urges that influenced the explorers are to desire to take hold of other land for territorial expansion.
Another very important thing to consider as well was the trading. One country had to exchange products to another country. Hence, there were need for them to cross the seas.
It was largely the Industrial Revolution that led to the growth of factories in England in the eighteenth century, since this was a time when the production of things like textiles was heavily increased.
