When we follow the evolution of thought in Religions,one can see a gradual development of Spirituality.
Man first feared Nature and worshipped it’s different aspects.
He assigned them super human powers.
He was scared of Fire,Water,Rains, Thunderbolt, Earthquakes.
He feared them ,appeased them and sought relief.
There were as many Gods as one feared.
On the other hand,when he found benevolent things in Nature,he included them also in the list of God’s.
The practice of worshipping many Gods is called Polytheism.
Hinduism has one essential difference while moving on from Polytheism.
One would find that One God is praised,while others are relegated to secondary or tertiary places in worship.
Thus we find Shiva worshipped as the Supreme Deity and other Deities pushed to secondary places.
The same with Vishnu,Brahma,Agni,Vaayu,Devi,Agni and others.
This practice of praising one God and pushing others back is called Henotheism.
Hinduism ultimately reached Monism,Non Dualism and Qualified Non Dualism,
But this article is on Polytheism.
Here many Gods are worshipped.
Though the Vedas do not advocate Idol worship ,Temple worship, they are followed nevertheless.
This practice was regulated by the Agamas,that is worship in Temples.
The Agamas ,which rose later to the Vedas lay down rules for building temples and methods of worship in Temples.
For details on Agamas,why many Gods in Hinduism,please read my articles on the same names.
In temple worship,one finds Presiding Deity, Moolavar and another Deity for taking out during auspicious occasions.
All poojas are performed first to the Presiding Deity Moolavar and then to the Utsavar.
This concept is unique to Hinduism.
While checking up the history of Pre Islamic Polytheism and method of worship, one finds that the Pre Islamic Deities were worshipped in the same way as that of Hindus in Temples,that is they had Moolavar and Utsavar.
Yet another proof of Hinduism being the forerunner of Pre Islamic Religion.
‘The pre-Islamic Arab religion was polytheistic, venerating many deities and spirits through statues, baetylus and natural phenomena. According to the Book of Idols, there are two known types of statues; idols (sanam) and images (wathan). If a statue was made of wood, gold, or silver, after a human form, it would be an idol, but if the statue was made of stone, it would be an image.
Reference and citation.
al-Kalbi, Ibn. The Book of Idols (1952 Nabih Amin Faris translation). pp. 12–13.