Old people fairly reliably vote. Young people often don’t.

Older folks liked Ed Gallrein. Massie appealed more to the younger demographic. The guy preferred by the people who vote regularly subsequently won.

Not all that exceptional or dramatic. Just mathematics. If I had to guess. Massie saw the polling. Realized he was underwater with the older folks. Subsequently dumped all his eggs in the younger voter basket hoping popularity online would translate to votes.