Anyway, several peoples have been living in what is today called "Nepal", for many thousands of years. They have spoken several languages, most of which are other than 'pure' sanskrit. And they have known and practiced Buddhism for a long time. Buddha encouraged the teaching of Dharma in the language spoken by normal people.
For example Licchavis, that are mentioned in the Vimalakirti sutra : "Licchavi (also Lichchhavi, Lichavi) was a kingdom which existed in the Kathmandu Valley in modern-day Nepal from approximately 400 to 750 CE. The Licchavi clan originated from Vaishali ancient India and conquered Kathmandu Valley." (
wikipedia)
Buddha was born in Lumbini in the Shakya Kingdom. Lumbini is considered to lie in present-day Rupandehi District, Lumbini zone of Nepal.
Buddhism during the Licchavi period (400-750 CE)
"The Licchavi period saw the flourishing of both Hinduism and Buddhism in Nepal. Excellent examples of Buddhist art of the period are the half-sunken Buddha in Pashupatinath, the sleeping Vishnu in Budhanilakantha, and the statue of Buddha and the various representations of Vishnu in Changu Narayan.
Another Buddhist text, the Mañjuśrī-mūla-kalpa, mentioned Manadeva as the King of Nepal Mandala. Researchers believe the Mulasarvastivadavinaya was written in the 2nd century CE, and that the Manjushrimulakalpa was written during Manadeva's reign. The Swayambhu Purana, the ancient Buddhist Purana text, and a Licchavi inscription all mentioned Nepal Mandala.
Buddhist inscriptions and chronicles and Tibetan sources also record a few tantric Buddhist deities, namely Akshobhya, Amitabha, Vajrayogini, Vajrabhairava, Usnisavijaya and Samantabhadra. Strong influence from Animism resulted in belief in Buddhist deities such as the Pancaraksas.
Religious tolerance and syncretism were stressed during the Licchavi period. King Manadeva paid homage at both Hindu and Buddhist sites. His family subsequently found expression for their beliefs in various religions.
The worship of the Caitya and the Rath Jatra cart festival of Avalokitesvara were introduced around this period
Many ancient sites in the Kathmandu Valley were identified with major Buddhist Caityas, such as Swayambhu, Boudhanath, Kathmandu and the four "Ashoka" stupas of Patan, and another two hundred stone Caityas dating from the Licchavi Period, were testified to the widespread antiquity of [Cetiya|Caitya] worship.
It is possible that this practice, in its earliest incarnation, was related to the worship of stones, which may have originated in the early, rival Kirata inhabitants of the Valley, prior to the Licchavis. According to one of the earliest Licchavi inscriptions, Caitya worship ordinarily consisted of ritual circumambulation of the caitya and offering standard items such as incense, colored powder, oil lamps and ablutions. At times, the inscriptions indicate, it could even involve resurfacing an existing Caitya and covering the new surface with many elaborate paintings.
Caitya worship was an important factor in bringing more of the proto-Newar tribal inhabitants into the Buddhist fold, as it was a devotional practice designed for the general public. Thus, the masses probably began practicing the cart festival of Avalokitesvara/Matsyendranath (Jana Baha Dyah Jatra and Bunga Dyah Jatra) during the latter half of the seventh century AD.
This festival was celebrated by hundreds or even thousands of people, who helped to construct and transport a huge, wheeled cart that bore the image of Avalokitesvara for several days or weeks along a specific route. The introduction of this festival must have been an instant success among the majority of the Kathmandu Valley population. This strengthened Buddhism's standing in relation to the other Hindu and Animist faiths of the Valley at the time.
Forty stone inscriptions made some mention of Buddhism throughout the Licchavi period. Most of the references are concerned with monasticism. However, almost nothing is known about the day-to-day life in the Vihara monasteries or how they functioned administratively.
The names of the fifteen Buddhist monasteries are known, and it is clear from the context in which some of these are named that they are among the most important religious sites of that time. It is not known for certain what schools of Buddhism were most prominent at the time. But the strongest early influences (aside from an even earlier probable substratum of Pali Buddhism) probably came from the Mahasanghika, Sammitiya and the Sarvastivada schools. The Madhyamaka and Yogacara schools were thought to be more influential in the later period with the emergence and growth of the Vajrayana school.
Inscriptional evidence also proves that there was a string of traditional methods of making religious gifts. These offerings were used for earning blessing and making merit, and the women of the Buddhist seem to have taken the lead in offering these gifts.
Strikingly, parallel points within the Buddhist cave contain inscriptions of Maharashtra, which predated the Licchavi Nepal. The references in the Licchavi inscriptions to the Mahayana and Vajrayana are mentioned in connection with Buddhist art and notable Buddhist figures of the Licchavi period."
https://en.wikipedia.org/wiki/Buddhism_in_Nepal
