Any reason? As far as vishnu goes, he preserves order of everything. In fact he is the direct manifest of Brahma, the creator of everything(or God itself)
You see that. LT summoned Vishnu to battle the Thanos with the Heart Of The Universe. Summoned him like a master would his dog. No disrespect to Vishnu, but that was the only analogy I could think of.
Haven't seen that one, but obviously the author has a misconeption of Vishnu and Hinduism, Vishnu is not even an entity and has no physical body, he can take anyform he wants.
And what happen when vishnu was summoned? Did he beat Thanos?