Isn't obvious they should first offer exotic food.

I mean, 'Whale' meat or 'Caviar' or 'Foie Gras' instead of ordinary 'Salmon' would find far more market.

Why would you think that? It's much more urgent to replace commonly eaten foods like beef, chicken and fish than foods that for most people are little more than a curiosity.

With that said, vegan caviar has existed for years make of algae, and it's honestly not far from the real thing.