Why did renaissance painters prefer the pigment made from lazurite over other blue pigments?

The correct answer is It gave a brilliant color and did not fade

Earlier versions of blue that were used by painters would fade overtime and what would be left would be a bad looking version of blue that had nothing to do with the original rich color. They discovered that if lazurite was used to get blue, that it would last for much longer and the richness would prevail without having to alter anything.