Why is there a system of checks and balances?

To limit the power of each branch. The reason it exists is to make sure that all of the branches, executive, judicial and legislative, don’t over do their power. For example, the executive, which is the president, doesn’t pass laws without congress or the house’s approval. They each balance themselves out.

(elizabeth's continuing support of english explores in the americas brought in vast supplies of silver and gold)

Well, because the resources were not biased.