Why did Booth kill Lincoln?

John Wilkes Booth grew up in Maryland. As an adult, he became an actor who, over time, became somewhat respected among critical circles. Though he spent a good deal of time in the North, including performing in New York, he considered the secession of the South a bold move. Unfortunately, that support put him at odds with many locals in the state. Booth was an opponent of abolition and personally attended the hanging of John Brown, the leader of the notable Harpers Ferry raid that was intended to create a slave revolt. Given his opposition to abolition and support of the secession, Booth was quite obviously a strong supporter of the South, including his home state of Maryland. Booth felt that President Lincoln was responsible for the war that was devastating the Confederacy and as early as 1864 began to come up with plans to kidnap the president.
Over the course of the Civil War, Booth’s opposition to the North and Lincoln himself grew more intense, to the point that he was arguing with family over the issue. The surrender of the Confederacy only served to enrage him even more. After the victory of the North and the end of the war, Booth used his status as a popular actor to access the area where Lincoln was seated and kill him. The assassination of President Lincoln was just the final step in a long history of supporting his home state of Maryland, the larger Confederacy, and hating the actions of the North and President Lincoln.

John Wilkes Booth was a passionate supporter of the Confederacy as well as slavery in the South, although he never joined the Confederate Army himself. He was also an accomplished actor who enjoyed high levels of success and popularity in the South. Booth (along with co-conspirators John Surratt, Michael O'Laughlin, and Samuel Arnold) was originally involved in a plot to kidnap Lincoln and deliver him to officials in the South. However, the kidnapping plot failed on two separate occasions.
Enraged by the surrender of the Confederate Army, John Wilkes Booth desired to eliminate Abraham Lincoln, whom he viewed as a tyrant. Booth also felt that Lincoln's Reconstruction policies, which included extending the vote to African Americans, would destroy the South. Motivated by political zeal and a desire for revenge, Booth successfully shot Lincoln at Ford's Theatre on April 14, 1865; Lincoln died at 7:22 am the next morning.
https://teachinghistory.org/history-content/ask-a-historian/24242

https://www.history.com/this-day-in-history/john-wilkes-booth-shoots-abraham-lincoln