This is a valid point in general, but for top tier currencies such as Doge, there are literally hundreds of exchanges with such orderbooks so it's not a concern

This is a valid point in general, but for top tier currencies such as Doge, there are literally hundreds of exchanges with such orderbooks so it's not a concern. Further, most large trades don't take place on exchanges public orderbooks, but on private OTC desks with separate books, for this reason. Generally, large buyers are matched OTC to large sellers at prices a little different to the on-market, but better than relying on on-market liquidity. The same happens in traditional finance, or anywhere. For example, if a taxi company wants to buy 1000 cars, they won't attempt to get them from the local yard.