Cruthaigh has other meanings also. One of them is to prove.
Cruthaigh an teoirim = Prove the theorem.
Do can mean 'to' or 'for' and 'for' makes more sense here.
See point 4 in do(3) here
Go raibh maith agat! I understand it know.
But Duo is not much for "sense", is it? It just feel that, if it is about literal translation, "I create a nice thing to you" should be accepted.