“There are some obvious reasons. More people live in cities now, and bedbugs love densely packed warm bodies. We’re also traveling more than ever before, giving bedbugs an opportunity to spread (see: horror stories of bedbugs in Airbnbs).
But the main reason why it’s boom time for bedbugs, according to the review, is that they’ve evolved resistance to many pesticides, our main line of defense. Indeed, these critters are now resistant to “most of the major classes of insecticides,” the review states, including pyrethroids, which is still one of the most commonly used insecticides. They’ve also developed resistance to DDT, which attacks insects in a similar way to pyrethroids.”
https://www.vox.com/down-to-earth/2023/10/15/23914204/paris-france-bed-bugs-infestation-outbreak