> The FDR admin had 90% support in the House and Senate.

FDR directly embedded his staff in Congress and told them what they were going to do, and vigorously attacked anyone who got in the way of his agenda by any means necessary, including using the FBI and IRS against them, denying them federal funds, etc. He also was very effective at bullying the press - look at what went on with radio licenses. He even (via the Black Committee and FCC) conducted mass surveillance on his political enemies.

FDR did have a lot of support in Congress but brutally punishing people is what made him effective. He was certainly one of the most authoritarian Presidents in American history and we should probably thank our lucky stars he was a good one.