I would be interested in his politics.
No wonder you didn't find anything on him. Back in those days, you either agreed to state politics, or you faced persecution, jail, torture and death eventually. There' was no such thing as your politics. Politics was a single one and you chose sides, depending on how brave you were.
He was critiqued and excluded from exhibitions, you can imagine he had no choice than to succumb, to be able to survive.