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It's very different from just anime waifus you masturbate onto. Having an Oshi is putting your Faith, Hope and Trust in someone whom you can't even be sure exists, but in turn, they give you happiness and inspiration to continue furthermore in the harsh realities of life. In essence, they become your Saviour. And as a result, you worship them more, support them in all their endeavours, proselytise for them, and crusade against the antis who dare slander their name. Because having faith in your Oshi not only gives her happiness and hope but also gives you happiness and hope. Every message is a prayer, every superchat an offertory, every merch a holy relic, every milestone, achievement or collab a miracle.
Heck Vtubing is like the marriage of anime and religion. More so than the Church of Madoka. It isn't just a pre-scripted anime girl to fap on, it's an anime girl you can actually worship and respond to your prayers.
Heck, that's one of the reasons I considered Kiryu Coco/Kson to fit the Messianic Archetype trope checklist. Her true biggest appeal is that she wants to help and save everyone, moreso than being a shitposting meme dragon. In Hololive, just ask Watame, Aqua, Marine and Haachama. She endured the Chinese persecution led by Judas (Artia) and forgave them, even choosing to die (graduation) for it. Now she in her resurrected form wants to save the Indie world and usher in Paradise (break the boundaries between corpos and indies), and even saved someone whom Japan had already given up on and on the verge of suicide (Mikeneko), even if it meant doing a Lelouch, i.e. by joining Vshojo as part of her plan, she became a reviled traitor and even painfully lost her most beloved (Kanata). Such a personality is unironically the definition of a hero, and deserves worship and admiration.
At the same time, there are false gods who'd fail you. I did it with Pippa, she became my inspiration in life because I relate myself to her too much, but it only ended in disaster, humiliation and betrayal.
Face it. In this modern secular world devoid of Gods and spirits, Vtubers have begun to fulfill the role. They are the Gods of the modern world. Thus, it is really fitting to call Vtubers Idols: for they are in the original theological definition, Idols.