It's interesting how lay people (typically not scholars or Indologists) underestimate the intellectual rigour and continuity of India's indigenous traditions.
They tend to apply the same framework they apply for the Middle East to India.
Iraqis forgot about Hammurabi, Ashurbanipal, et al., Egyptians forgot about Khufu, Hatshepsut, et al.; Arabs forgot about Gindibuʾ, Karibʾīl Watār, et al.
These figures were (re)discovered by archaeologists and epigraphers in the 18th-20th centuries.
The accounts of az-Zabbāʾ/Zenobia in medieval Islamic historiography drew from both indigenous (Arab, Syriac) & Greco-Roman/Byzantine sources while the account of Dārā (Darius III) in Firdawsī's Šāhnāmah drew almost entirely from the Alexander Romance tradition (via Syriac translations from Greek, which were later translated into Pahlavi/Middle Persian)
Therefore, it must stand to reason than Indians also must've forgotten the names of rulers like Candragupta, Aśoka, etc. prior to the arrival of Westerners, no?
Yet this is clearly not true.
Although the Brāhmī script used in the inscriptions had changed so much as to be unrecognizable, Candragupta (Sandracottus of the Greeks) was well known through texts and plays like Viśākhadatta's Mudrārākṣasa, which were completely independent of Greco-Roman sources like Megasthenes.
The names of Aśoka Maurya and his sons Daśaratha and Samprati are recorded in the Puranic vaṃśāvalis and he is glorified in Buddhist sources such as the Divyāvadāna (which contains a section known as the Aśokāvadāna) and Srilankan chronicles like the Dīpavaṃsa and Mahāvaṃsa.
A manuscript of the Divyāvadāna in Sanskrit (or Sanskritized Prakrit) was discovered in Nepal in 1824, so the text was continually being copied.
One could argue that modern Persians had no knowledge of Old Persian for over 1,500 years (until the script was deciphered in the 19th century) and minimal knowledge of Avestan.
The Zand and Dēnkard commentaries composed by medieval Zoroastrians dasturs and mobeds often differs from modern philological readings.
Yet in the case of the Vedas, there is a largely unbroken chain or recitation reinforced by the śikṣās, prātiśākhyas, etc. and interpretation based on the Nirukta (the Naighaṇṭuka, Naigama, Daivatakāṇḍa-s of Yāska), Vyākaraṇa (Aṣṭādhyāyī Vārttikas Mahābhāṣya, along with the Uṇādisūtras and Phiṭsūtras), etc.
Therefore, the commentaries by Bhaṭṭabhāskara, Sāyaṇa, Veṅkaṭamādhava, Skandasvāmin, Mahīdhara/Uvaṭa are quite close to modern philological interpretations, simply because formal study of Sanskrit (including Vedic Sanskrit) never truly disappeared in India.
Even the study of the medieval Prakrits never disappeared among the Hindus and Jains.
Most people nowadays think of the 16th century grammarian Mārkaṇḍeya as the final Prakrit grammarian, yet Rāmaśarman Tarkavāgīśa composed his grammar of Prakrit and Rāmapāṇivāda composed his Kaṃsavaho and Usāṇiruddho less than two centuries before Norwegian-born German Indologist Christian Lassen's published his Institutiones Linguae Prakriticae.
When it comes to continuity, one can't treat the Indian Subcontinent the same way as the Middle East, Iran, or Central Asia, yet the fact that they rehash the same arguments regardless just highlights that these sorts of arguments (whether applied to India OR the Middle East) are ultimately rooted in racial paternalism ("the White Man's Burden," yet applied to history).
Claim 1: "Understanding & translation of the Rig Veda had to be done by Westerners because much was lost in India"
Status: False. Vedas were never "lost" in India. They were preserved through a complex, oral transmission system (incl. permutations) for millennia,