Here is how it is explained by Jim Holt in his book “Why Does the World Exist?”:
“…space is not nothing. Nor is the space of the quantum vacuum really empty.
It has a complicated mathematical structure; it bends and ﬂexes like rubber; it is saturated with energy ﬁelds and seethes with virtual-particle activity.
The quantum vacuum is a physical object; indeed, it is a little proto-cosmos unto itself.”
In quantum mechanics, the vacuum contains electromagnetic waves and particles that pop into and out of existence.
In this tenuous world, a mechanical Universe looks pretty unlikely as a metaphor.