Is there an alternate proof or an exposition of: Exponential lower bound for $\Sigma\Pi\Sigma$ circuits [Grigoriev-Karpinski(1998)]? Is there an alternate proof or an exposition of the result of Grigoriev and Karpinski (STOC 1998, doi:10.1145/276698.276872) on the exponential lower bounds for Depth 3 arithmetic circuits computing $\mathsf{DET}_{n\times n}$ over a fixed finite field?

I could not understand section 2 of the paper. What is the intuition behind considering the F-linear operator $T_g$?
There was a subsequent extension by Grigoriev and Razborov (PS) that has a shorter exposition of proof.