It’s possible that there is a deeply sentimental streak in Polonius. To him, it perhaps seems that Hamlet really does love Ophelia and has gone mad because Polonius has thwarted his attempts to reach her. There’s a Polonius that looks at Hamlet and feels very sorry for his own actions, that perhaps sees himself in a young man grown crazy for love. Perhaps this reunion with Ophelia is an attempt to right his own perceived mistake.
And what if this whole scene is an attempt at reconciliation, what if it were filled with tenderness? What if all Polonius really wants to do is sit down with Hamlet and say, “There, there, young lover. I understand. It’s my fault. I didn’t realize how much you loved my Ophelia. Be patient. We’ll work it out.”
I’ve never seen it played this way but I’d like to.