It is entirely possible that the collapsing runner(or any collapsing runner) had some underlying medical issues. Women are more prone to anemia than men are and iron levels are even lower during certain points in the menstrual cycle. I collapsed in one race in my entire high school and collegiate career and it was XC regionals. I was always anemic, with irregular periods and I somehow managed to get my period for the first time in months the week of regionals. I think it definitely played a part in my collapsing.
Though it did not happen till after the finish line. I'm pretty sure I collapsed over the timing mat but I've been unable to find any footage