Isaiah 5:14
Therefore Sheol has enlarged itself
And opened its mouth beyond measure;

Sheol is a Hebrew word commonly translated as hell in King James. When the Hebrew text was translated into Greek, as the Septuagint, Hades was used.
I’ve read many sources that say Sheol and hades are the grave. Luke 16:19-31 is a story Jesus told of two men that died. One ended up in Hades in torment from fire.
Sheol and Hades are more than just a grave.
Revelation 20:14 says Death and Hades (hell-KJV) were cast into the lake of fire. This is the second death.
Isaiah says Sheol/Hades has grown larger.
How can this be?
Rebellious hearts of people!
Unrighteous behavior!
Sin!
The world population at the time of Isaiah was far, far less than the 7.7 billion people of today. I seriously doubt that one-half billion existed since the world population did not reach one billion until 1804 A.D.
If only half the people die and go to hell then that’s 250,000 out of half a billion. Today that number is almost 4 billion.

As Christians, our work is cut out for us. We can do nothing to empty Sheol of those already present, like the rich man of Luke 16. However, we can prevent others from going with a presentation of the Gospel and a call for personal salvation.
If we don’t, sheol/hades will continue to grow larger.