Oscar worthy for Frank ?

I saw the film when I was only 10 and was mesmerized. I just saw it again after about 60 years and it still is remarkable. I could never understand why Frank never won the Oscar for this performance. Ernest Borgnine was good as Marty but was nowhere in comparison to Franks' performance. Why did Frank lose ? Was it due to his association with certain Mafia figures or because of his support for Israel? Who Knows? It's well-known that Frank had some enemies in Hollywood.