Luke tells us that he interviewed the surviving witnesses of the events he described, including (presumably) Mary. Since there is no further mention of Joseph after Jesus’ adolescence, I presume that he was not alive when Luke wrote, so the fact that Mary would be the source for Jesus’ birth and childhood narratives is plausible, but it doesn’t mean she wrote it (she was likely illiterate after all). Why do people feel the need to make up crap that the written Scriptures don’t support?
To publish articles and get tenure.