It is tempting to agree with the author's analysis that when people pray to Ganesha, they are not really praying to some elephant headed God sitting in the sky, but to the personification of the quest for knowledge.
However if that is true, why do the prayers end at the conclusion of the 10 or 14 day Ganeshotsav and why is the personification of knowledge submerged in the sea? How many devotees really make that distinction?
Your ignorance to common Hindu way of life is profound. Have you ever been to any Hindu home? The common people's home? Not the uber elites. In a common hindu's home you most definitely will find a shrine devoted to our Dev & Devis, where everyday puja is offered, prayer is made. Well, not with so much colour and pomp as during Ganesha Utsav, as that is not practical to carry on day to day life. For that we have temples, where we go to pray on special occasions. See either Hindu religion or in extension, it's dev and devis are not as stuck up as other gods in other religion, and they don't claim our obeisance at every step. But our gods are never far from us. In every endeavour we pray their blessings. That is a short example of a Hindu.
And immersion of Idol is a way of saying goodbye to Shri Ganesha from the festival and celebration, not from our lives. He is always with us, and the period of Ganesha Utsav is our way of celebrating his glory with a grand fashion, that displays our prosperity which has come because of knowledge we have received by his blessing.
Is it required for every person to logically dissect his faith? Whether distinction is made or not, only the rarest of fools believe that on the hall of examination the deva will himself write the papers or make a stupid deal to make profit. Well, thankfully those fools convert themselves!!!