Would you necessarily know if they were successful? Can you actually prove that not a single person in that convention accepted some kind of kickback for e.g. changing their vote?
Mechanisms that effectively prevent this do exist in the literature, to be clear, but I rarely hear of those ones actually getting implemented.
Well we mostly know what positions these groups were pushing for. It's possible that some influence went unnoticed.
That said, the US used to have quite a lot of juror bribery in the late 1800s and managed to successfully crack down on it with harsh penalties, sting operations, and other strategies. Attempting to bribe a juror can get you 15 years in federal prison in the US, it's not taken lightly.