Answer by taking a quote from the following article:

The Grand Ole Opry is a weekly country-music stage concert in Nashville, Tennessee, which was founded on November 28, 1925, by George D. Hay as a one-hour radio "barn dance" on WSM. Currently owned and operated by Opry Entertainment (a division of Ryman Hospitality Properties, Inc.), it is the longest-running radio broadcast in US history. Dedicated to honoring country music and its history, the Opry showcases a mix of famous singers and contemporary chart-toppers performing country, bluegrass, Americana, folk, gospel, and comedic performances and skits. It attracts hundreds of thousands of visitors from around the world and millions of radio and Internet listeners.

Following the departure of the Opry, Ryman Auditorium sat mostly vacant and decaying for twenty years. An initial effort by National Life & Accident to tear down the Ryman and use its bricks to build a chapel at Opryland USA was met with resounding resistance from the public, including the influential musicians of the time. The plans were abandoned, and the building remained standing with an uncertain future. Despite the absence of performances, the building still held such significance as an attraction that it would remain open for tours.  In 1991 and 1992, Emmylou Harris performed a series of concerts there and released some of the recordings as an album entitled At the Ryman. The concert and album's high acclaim renewed interest in reviving Ryman Auditorium as an active venue. Beginning in September 1993, Gaylord Entertainment undertook a full renovation of the Ryman, restoring it into a world-class concert hall that reopened with a broadcast of A Prairie Home Companion on June 4, 1994.  On Sunday, October 18, 1998, the Opry held a benefit show at Ryman Auditorium, marking its return to the venue for the first time since its final show on March 15, 1974. The show was well received by fans, performers, and management alike, and so the decision was made to host the Opry's regular shows there on January 15 & 16, 1999 as part of the celebration to commemorate 25 years at the new venue.  Beginning in November 1999, the Opry was held at Ryman Auditorium for three months, partly due to the ongoing construction of Opry Mills. The Opry has returned to the Ryman for the three winter months every year since, allowing the show to acknowledge its roots while also taking advantage of a smaller venue during an off-peak season for tourism. While still officially the Grand Ole Opry, the shows there are billed as Opry At The Ryman. From 2002 to 2014, a traveling version of the Radio City Christmas Spectacular took up residence at the Grand Ole Opry House each holiday season while the Opry was away. It was replaced by Dr. Seuss' How the Grinch Stole Christmas! The Musical beginning in 2015.

How was it revived?
In 1991 and 1992, Emmylou Harris performed a series of concerts there and released some of the recordings as an album entitled At the Ryman.