That's not what that says. The graph that tops out at 42% is talking about the effective tax rate, not marginal. It's perfectly possible that some people had part of their income taxed at 70%, but their effective tax rate was 42%. That's just how marginal tax brackets work.
It entirely possible but no one was paying the 91% rate. The broader poor was that these rates weren’t effective. Reported income is highly elastic, according to work by Saez et. al.
