Brett Weinstein explained it really clearly on the Rogan podcast which you had linked to here on VCT. IIRC he said that when the "vaccine" doesn't stay in the shoulder muscle after injection like it is supposed to, the spike protein in the "vaccine" can migrate to the heart via the circulatory system and lodge there. Then, a person's immune system will then interpret the heart as a foreign object and start attacking it because the spike protein lodged along the surface of the heart signals the immune system that the heart is a foreign object, causing inflammation, and increasing the chances of a heart attack as a result. I suppose that in a young healthy person, the immune system is very powerful, so the immune response is a lot greater.