They are Masters because of their realization on emptiness of the mind

And then Vidyadharas, of course, means the noble ones, the high beings, high masters. So, this is the meditation of the teaching of Longchen Nyingthig practices. All the Vidyadharas of this lineage are very great, compassionate and have wisdom, and Mahasiddhas, so therefore they called Vidyadharas. Vidyadhara basically means the one who’s able to hold the teachings of the essence or the nature of the mind, who’s realized the nature of the mind, who became enlightened through realizing the nature of the mind. They are the Vidyadharas.

So, Vidyadharas is another way of calling the Lineage Masters. They are not just master, but great masters, very accomplished masters on the path of liberation, on Dharma practice. Any teacher, any person, who has students, we sometimes called them master. But this master has a different meaning: It’s the Master because of their realization on emptiness of the mind, nature of the mind, so therefore Vidyadhara is something with very special meaning and special name.

Hungkar Dorje Rinpoche, “Vidyadharas“