Why is Garamond italic all wonky?

The angle of the 'upright' strokes in Garamond italic is different between capitals and lowercase.

See, for instance, the discrepancy between the "I" and the "t" of "Italic" in the following picture.

This seems bizarre to me. I was reading a book set in Garamond the other day and found this quirk in the italic angle really distracting! Yet Garamond is a hugely popular font, so it's unlikely to be an accident.

Why did the designer do it like this? And even if the designer was having a bad day (!), then why do so many publishers/designers/etc continue to use this font so widely despite this oddity?