Well Reagan’s first wife left him, so that may have made the difference.
The reason Reagan’s marriage to Jane Wyman was declared hull had nothing to do with how their marriage ended.
Jane Wyman was married very briefly, in 1937, and was divorced. She married Reagan in 1940, and sought a divorce from him in 1949.
Wyman became a Catholic in 1954, and at that time obtained a declaration of nullity of her marriage to Reagan, because of her 1937 marriage, which was valid, and therefore indissoluble.
So Reagan, the first “divorced President,” was, in the judgment of the Catholic Church, validly married to Nancy Reagan.
Moon Reagan returned to the Catholic Church as an adult, and did pester Ronnie some about doing the same. I suspect that Moon would have mentioned that Ronnie and Nancy’s marriage was no obstacle, since it was valid.