Two words: DDT ban.
You are correct. In the early 20th century bedbugs were eradicated with DDT. Sleep tight and don’t let the bedbugs bite.
Nahh. Bedbugs became resistant to DDT decades ago.
In the 90s the EPA banned malathion and propoxur. Which are still quite effective against bedbugs but illegal to use.
Bedbugs have been bouncing back ever since.
To be fair, malathion and propoxur can be pretty nasty.