Why has the Church of Scotland lost 1 million followers since 2001?

The latest 2022 census of Religion in Scotland shows that there has been an increase from 28% of non-religious people in Scotland (in 2001) to 51.1% (in 2022). The largest decrease has come mainly from Protestant denominations with the Church of Scotland having lost 1 million followers since 2001. The census shows that 2,780,980 persons who participated self-identified as having no religious beliefs (51.1%). The total of all the Christians in Scotland who participated in the census is 2,110,405 (38.8%). My specific question relates to the Church of Scotland (which is Protestant) and why 1 million have left the church since 2001. Is there any documentation to explain why this has happened? General apathy and secularism cannot be the reason that the decline in membership is much steeper in the Church of Scotland than in the Catholic Church, for example.