Brief history of the decline:
2013: Boy Scouts ends ban on gay scouts
https://www.nytimes.com/2013/05/24/us/boy-scouts-to-admit-openly-gay-youths-as-members.html
Membership 3.03 million
https://filestore.scouting.org/filestore/annualreport/2013/324-168_WB.pdf
2015: lets in gay leaders
https://www.cnn.com/2015/07/27/us/boy-scouts-gay-leaders-feat/index.html
Membership at 2.74 million
https://filestore.scouting.org/filestore/annualreport/2015/2015_Annual_Report.pdf
2016: libs report Boy Scouts doing great after ending gay ban
https://apnews.com/article/3de59dad2ba74b8f98bd3bc9b93c9bfc
Membership at 2.714 million
https://scoutingwire.org/annual-report-2016/
2017: announces will let in girls, will allow them to obtain Eagle badge
https://www.nbcnews.com/news/us-news/boy-scouts-will-admit-girls-allow-them-earn-eagle-scout-n809836
Membership at 2.659 million
2018: changes name to scouts BSA because it now lets in girls. https://www.npr.org/sections/thetwo-way/2018/05/02/607678097/boy-scouts-changing-name-to-scouts-bsa-as-girls-welcomed-into-program
Membership at 2.499
https://ar2018.scouting.org/wp-content/uploads/2019/05/BSA-2018-AnnualReport_1.pdf
2019: girls officially start being accepted as Boy Scouts
Membership at 1.97 million
2020: membership at 1.12 million
"The Boy Scouts of America said this week that the organization would create a “diversity and inclusion” merit badge and make earning it a requirement of becoming an Eagle Scout, the highest scouting rank." https://www.nytimes.com/2020/06/17/us/boy-scouts-diversity-inclusion-eagle.html
2021: membership at 762,000
Sheesh, losing 75% of your membership in less than 10 years.