Analysis of information sources in references of the Wikipedia article "Art of Mathura" in English language version.
These are ample reasons to believe that the aniconism of early Buddhist art was rooted in Vedism in which the highest Gods were conceived as impersonal forces and amūrta, without form.
There is strong archaeological evidence in favour of Mathura being a centre of Buddhist religious activities (and not Vaishnava worship) during the Gupta period. (...) In fact the Hindu images which appear at Mathura in the pre-Gupta days are very few in number...
We should do well to remember that the Aryans worshipped purely the elementary forces of nature by means of elaborate sacrifices, together with appropriate hymns. In this scheme of ritual it was not necessary, nor was it possible to substitute the object of exaltation so convincingly by any concrete form, least of all by human figure, without compromising the fundamental attitude of the worshipper to the all-pervasive power that was being propitiated. Such a change in the approach of the tightly-knit Vedic and even post-Vedic society, orchestrated as it was by orthodox priesthood, could not have come of itself. This was possible when such an urge was actually felt by the general masses and that feeling was intensified by the ideological impact of fresh ethnic influx into the Indian social pool.
English translation: "Towards the middle of the 6th century, the activity of the Mathura school abruptly ceased, undoubtedly following the ravages of the Huns who had invaded the Gupta empire around 455. It must have died with the art of Gandhara under the persecutions by Mihirakula"
French original: "Vers le milieu du VIe siécle, l'activité de l'école de Mathura cesse brusquement sans doute à la suite des ravages des Huns qui avaient envahi l'empire Gupta vers 455. Elle a dû mourir avec l'art du Gandhara sous les persécussions de Mihirakula"
We should do well to remember that the Aryans worshipped purely the elementary forces of nature by means of elaborate sacrifices, together with appropriate hymns. In this scheme of ritual it was not necessary, nor was it possible to substitute the object of exaltation so convincingly by any concrete form, least of all by human figure, without compromising the fundamental attitude of the worshipper to the all-pervasive power that was being propitiated. Such a change in the approach of the tightly-knit Vedic and even post-Vedic society, orchestrated as it was by orthodox priesthood, could not have come of itself. This was possible when such an urge was actually felt by the general masses and that feeling was intensified by the ideological impact of fresh ethnic influx into the Indian social pool.