Why did the British government made an agreement with the US by giving away Maine during the Treaty of Ghent even though about all of the battles in Maine that the British and Canadian forces fought were entirely successful. What prevented the British to seize to control Maine. Yes of course, the British was also trying to seize control other territories in North America (such as Louisiana and the Ohio Valley for example) but I want focus on Main for right now. Even the smallest reliable territory can make a huge changes throughout history. https://en.wikipedia.org/wiki/War_of_1812 https://nationalpost.com/news/canada/new-ireland-how-maine-almost-became-part-of-canada-at-the-end-of-the-war-of-1812
It has to do with the British war aims. To wit, there was no interest, popular or political, in re-conquering the United States. For the British, the War of 1812 was a defensive action fought in the shadow of the Napoleonic threat. The British were interested in ending the war almost as soon as it began, and in the aftermath of their failed invasion of northern New York at the Battle of Plattsburgh, the British felt like quitting while they were ahead, to make a long story short.
Maine was not the only territory the British controlled at the end of the war, either, but they returned all conquered territory to the United States, preferring to end the war and restore the status quo antebellum.
I have written elsewhere about political goals of both sides, and I'm happy to answer follow-ups.
Coincidentally, today is the anniversary of the signing of the Treaty of Ghent! The treaty was also called the "Peace of Christmas Eve."