Indra is far superior in the Vedas. In rig Ved more than a quarter of hymns are dedicated in praise to Indra alone. Whereas Vishnu has barely 5 hymns alone and 4 more shared with Indra.
As per the Atharva ved, Skambha is the cosmic pillar which supports the universe and upon which Prajapati established and supports creation.
AV 10.7.7
यस्मिन् स्तब्ध्वा प्रजापतिर् लोकान्त् सर्वां अधारयत् । स्कम्भं तं ब्रूहि कतमः स्विद् एव सः ॥
"Tell me, who is that Skambha upon whom Prajāpati established and firmly supported all the worlds?"
Av 10.7.8
यत् परमम् अवमम् यच् च मध्यमं प्रजापतिः ससृजे विश्वरूपम् । कियता स्कम्भः प्र विवेश तत्र यन् न प्राविशत् कियत् तद् बभूव ॥
"That universe, with all its forms, highest, lowest and middle, which Prajāpati created: how much of it did Skambha pervade, and how much remained outside?"
Indra is identified with this cosmic pillar. Further the Cosmic order, Rta is itself constituted in Skambha.
Atharvaveda 10.7.29
In Skambha are the worlds, in Skambha is austerity, and in Skambha is established Ṛta. O Skambha, I know you directly; everything is contained in Indra."
Atharvaveda 10.7.30
इन्द्रे लोका इन्द्रे तप इन्द्रेऽध्यृतमाहितम् । इन्द्रं त्वा वेद प्रत्यक्षं स्कम्भे सर्वं प्रतिष्ठितम् ॥
"In Indra are the worlds, in Indra is austerity, and in Indra is established Ṛta. O Indra, I know you directly; everything is established in Skambha."
Vishnu's rise is much later, in the late Vedic period to further age of epics and Puranas ..