I don't think it's quite fair to call Polonius a fool, and I don't believe that Shakespeare intended him to be regarded as a fool. Hamlet refers to him as a fool where he says, "These tedious old fools!" but even Hamlet may not mean it literally. Polonius is getting old and exhibiting some of the characteristic of old people generally. For one thing, he talks too much. On one occasion Gertrude interrupts him by saying, "More matter, with less art." He is also forgetful, like a lot of old people. When he is talking to the servant he is sending to France to keep an eye on Laertes, he loses his train of thought and has to be reminded of what he was saying. Perhaps at one time he was exceptionally intelligent. After all, he has risen to the post of advisor to the king. His problem might be diagnosed as senility. Hamlet can make him look foolish, but this is the sort of thing that some young men enjoy doing with old men. A notable example is where Hamlet asks Polonius, "Do you see yonder cloud that's almost in shape of a camel?" He gets the poor old man spinning around to look up at the sky until he is dizzy.
And thank you for your answe btw ^
Do you think you can regard him as the hypocritical fool? As in Act 1 scene 3 you see him acting a picture perfect father to both his kids Laeretes and Ophelia. He wishes the best for Laeretes in his new independent life and studies in Paris, and gives him quality advice. And for Ophelia you seem him demonstrate protection and care for her as a father should.
Shortly after you see Polonius denote both of these acts of fatherlyhood. In the beginning of Act 2 the audience witnesses him scheming with Reynaldo to infiltrate Laeretes privacy and check in on what he's up to. And as for Ophelia after she confesses her recent "awkward" encounter with Hamlet, Polonius apologizes, but we see the apology rather superficial and skin-deep. He is, not sorry for her hurt or discomfort, only that Hamlet’s madness has indeed been proven and is now a cause of concern for the realm.