Did all the people who died before Jesus go to hell?
The short answer
Before Christ opened heaven, all the dead went to "hell" in the sense of Sheol, the abode of the dead. But the just were comforted in "Abraham's bosom," apart from the damned, and Christ descended to free them.
By his death and Resurrection Jesus opened heaven (CCC 1026). Before then everyone who died went to "hell," but the just went to a part of it called "the bosom of Abraham," where they were comforted.
The parable of the rich man and Lazarus (Luke 16:19-31) suggests two parts: both men died, but Lazarus was comforted in Abraham's bosom while the rich man was in torment, with a great chasm between them.
The Catechism explains that Scripture calls the abode of the dead "hell" (Sheol or Hades) because those there lack the vision of God. This was the state of all the dead, evil or righteous, awaiting the Redeemer, though their lot was not the same, as the parable shows. Christ descended to free the holy souls who awaited him in Abraham's bosom, not to deliver the damned or destroy the hell of damnation (CCC 633).