Final answer:
The change in attitude among the congressional delegates can be attributed to the skirmishes at Lexington and Concord, the rejection of the Olive Branch Petition, and the realization that independence was the only viable option.
Step-by-step explanation:
The change in attitude among the congressional delegates from not advocating a break from Great Britain in the First Continental Congress to adopting the Declaration of Independence less than two years later in the Second Continental Congress can be attributed to several factors. Firstly, the skirmishes at Lexington and Concord in April 1775 had made it clear that reconciliation with Britain was no longer possible.
Secondly, the Olive Branch Petition, sent by the Congress to the British government in the hope of finding a peaceful solution, was rejected by King George III. Lastly, the escalating tensions and the realization that independence was the only viable option for the American colonies ultimately led to the adoption of the Declaration of Independence in July 1776.