Imagine if you could only buy bread with crypto, and some billionaire buys a large amount of crypto the night before, the next morning your bread will cost twice as much.
I don't think this is really a valid point. A situation where bread can only be bought using crypto would be very different to the situation we are in today. For a start it would mean that crypto had become fully integrated with mainstream society, and was used by everybody, all the time. Crypto would be vastly - multiple orders of magnitude - bigger than it is today. Look at how the price of small cap alts can be manipulated very easily, and at how much more difficult it is to manipulate the price of bitcoin, with its much higher market cap. In general the bigger a thing is, the more difficult it is to manipulate the price. As an example, if 1 bitcoin was worth $1 million, then $1 billion would only buy 1000 bitcoins, perhaps enough to move the price a bit, but no more than a $1 billion purchase in traditional markets would do.