Because what we really needed was more confusion in the iPad range! The Air's existence is already questionable as the only practical difference between that and the Pro is 120hz, which is nice but not worth the extra $$$.
Apparently, Apple plans to overhaul the iPad Air, having upgraded the mid-range tablet to its M1 SoC last year. According to new rumours, the next iPad Air will arrive in two variants, with a new larger size designed to fill the gap between its mid-range and flagship tablets that exists in its current product stack.