The Vedas, including Rig Veda 5.2.11, were composed by Rishis. They did not come down from heaven. So the question boils down to how a book written by humans can be considered to be divine. The answer is that the spiritual information contained in the Vedas is not the product of the intellect of the Rishis but have been discovered through deep meditation. It is in this sense that the Vedas are considered to be anadi (eternal) and divine.
There was a time when the Vedas themselves were considered eternal in
the sense in which the divine truths contained therein were changeless
and permanent and were only revealed to man. At a subsequent time, it
appears that the utterances of the Vedic hymns with the knowledge of
its meaning was important; and it was held that the hymns themselves
must have had a divine origin. At a still later period, the meaning of
the hymns showed that many of them could not be of divine origin,
because they inculcated upon mankind performance of various unholy
acts, such as torturing animals; and we can find many ridiculous
stories in the Vedas. The correct meaning of the statement "The Vedas
are beginning less and eternal" is that the law or truth revealed by
them to man is permanent and changeless. Logic, geometry, chemistry,
etc., reveal also a law or truth which is permanent and changeless and
in that sense they are also beginning less and eternal. But no truth
or law is absent from the Vedas, and I ask any one of you to point out
to me any truth which is not treated of in them.
(Complete Works of Swami Vivekananda, Vol.5: With the Swami Vivekananda at Madura, pp.205-206)
The Hindus have received their religion through revelation, the Vedas.
They hold that the Vedas are without beginning and without end. It may
sound ludicrous to this audience [in the West] how a book can be
without beginning or end. But by the Vedas no books are meant. They
mean the accumulated treasury of spiritual laws discovered by
different persons in different times. Just as the law of gravitation
existed before its discovery and would exist if all humanity forgot
it, so is it with the laws that govern the spiritual world. The moral,
ethical, and spiritual relations between soul and soul and between
individual spirits and the Father of all spirits were there before
their discovery, and would remain even if we forget them.
(Complete Works of Swami Vivekananda, Vol.1: Paper on Hinduism, pp.6-7.)
The Vedas are anadi, eternal. The meaning of the statement is not, as
is erroneously supposed by some, that the words of the Vedas are
anadi, but that the spiritual laws inculcated by the Vedas are such.
These laws, which are immutable and eternal, have been discovered at
various times by great men or rishis, though some of them have been
forgotten now, while others are preserved.
(Complete Works of Swami Vivekananda, Vol.6: Notes Taken Down in Madras, 1892-93, p.103)