Formerly, all activities were performed in connection with Vishnu, but after Satya-yuga there were symptoms of disrespectful dealings among Vaisnavas. Srila Bhaktivinoda Thakura has said that a Vaisnava is he who has helped others become Vaisnavas. An example of one who has converted many others into Vaisnavas is Narada Muni. A powerful Vaisnava who has converted others into Vaisnavas is to be worshiped, but because of material contamination, sometimes such an exalted Vaisnava is disrespected by other, minor Vaisnavas. When great saintly persons saw this contamination, they introduced worship of the Deity in the temple. This began in Treta-yuga and was especially prominent in Dvapara-yuga (dvapare paricaryayam). But in Kali-yuga, worship of the Deity is being neglected. Therefore chanting of the Hare Krishna mantra is more powerful than Deity worship. Sri Chaitanya Mahaprabhu set a practical example in that He did not establish any temples or Deities, but He profusely introduced the sankirtana movement. Therefore Krishna consciousness preachers should give more stress to the sankirtana movement, especially by distributing transcendental literature more and more. This helps the sankirtana movement. Whenever there is a possibility to worship the Deity, one can establish many centers, but generally one should give more stress to the distribution of transcendental literature, for this will be more effective in converting people to Krishna consciousness.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Seventh Canto, Chapter 14 – Text 39