Six onion-roof towers supporting heavens

[Jorge_Stolfi]

The domes (onion-shaped) are of Swiss-Italian origin. The church was built to bring the headquarters of the Eastern Roman Church from Istanbul to Moscow, which did not happen. The main church is still the Hagia Sophia, built on the Roman model of the Pantheon.
The roofs of the towers were planned to be spherical. However, the high snow load in the region would have caused the spheres to collapse. For this reason, the domes were designed to taper at the top so that the snow would not accumulate.
The planning took place around 1480. Therefore, the VM shape cannot have anything to do with the churches.

Not according to Wikipedia:

"It is not completely clear when and why the onion dome gained popularity in You are not allowed to view links. Register or Login to view., but buildings featuring them appeared as early as the 13th century,"

"The site of [St. Basil's cathedral] had historically been a busy marketplace between the St. Frol's (later Saviour's) Gate of the Moscow Kremlin and the outlying posad. The centre of the marketplace was marked by the Trinity Church, built of the same white stone as the Kremlin of Dmitry Donskoy (1366–68) and its cathedrals. Tsar Ivan IV marked every victory of the Russo-Kazan War by erecting a wooden memorial church next to the walls of Trinity Church; by the end of his Astrakhan campaign, it was shrouded within a cluster of seven wooden churches. According to the report in Nikon's Chronicle, in the autumn of 1554 Ivan ordered the construction of the wooden Church of Intercession on the same site, "on the moat".[14] One year later, Ivan ordered the construction of a new stone cathedral on the site of Trinity Church to commemorate his campaigns. Dedication of a church to a military victory was "a major innovation"[7] for Muscovy. The placement of the church outside the Kremlin walls was a political statement in favour of posad commoners and against hereditary boyars."

And the Panteon dome is a single piece of massive concrete, while that of Hagia Sophia is made of bricks and mortar.

All the best, --stolfi