Hi there!
Well, there are a lot of reasons. But I only remember some of them.
So the reasons are:
1) England/ Great Britain used to have large amounts of iron and coal.
2) They had textile industry. This makes them rich and powerful.
3) Huge commercial power. They used to have a lot of slaves from Africa and the Caribbean to make tea, tobacco for them.
4) England located in a perfect spot. The climate benefit their agriculture industry. They were able to produce more food and people were able to find jobs.
5) They had large sources such as sugar plantations. They used the slaves to make that happened.
There might be more reasons. But I hope I helped.
Good luck!