Any networks that both accept the prefixes and see these advertisements as the best path will send their traffic towards the route leaker, who will lack the capacity to handle this traffic, effectively blackholing these routes.

In theory, a large portion of the Internet would have still seen the legitimate routes as better paths, as they would have a shorter AS path (fewer networks in between) than the leaked ones. However, many networks often implement other BGP metrics for traffic engineering, depending on whether they are seeing the routes from a transit/peer/downstream customer, which may override the shortest AS path.