Some would say it was because Guru Arjan was siding with Jahangir's son who was trying to rebel. Others would say that it was because Guru Arjan was getting a following in Punjab and that Jahangir was insecure of his own hold on power and decided to execute Guru Arjan, but he is succeeded by his son Shah Jahan, who becomes decisively less tolerant. His reign, however, is known as the golden age of Mughal architecture with the crowning achievement, arguably, the Taj Mahal, which is a mausoleum that he commissions in the 1630s to house the body of his dead wife. As you can see here, it's housed in Agra, and Agra and Delhi, at various points during the Mughal Empire, are the capital. There's a few moments when it is at Lahore. He is eventually imprisoned by his son, Aurangzeb. Aurangzeb is considered a very strong and authoritarian ruler.