A 60° wash will kill them and eggs (needs to be a good 30 minutes at high temp). Same for tumble dry: 30+ minutes on high, eco dry won't bother them. Steam works, too, same principle: must be scalding and 20 minutes or more.
Insecticides don't hurt them these days.
Freezing for 4 or more days inactivates them, but eggs can survive so you must was the items as soon as they're out of the freezer. Also, make sure you freeze the things inside fully-sealed bags as the adults could find their way out.
Substances with very pointy molecules can kill most creatures with an exoskeleton, the points pierce their 'armour'. Salt does it, and so does diatomaceous earth - it's what they make clay kitty litter with, but you can buy it as a fine powder in huge bags. Diatomaceous won't harm fabrics or plants like salt does, but you must hoover it all up or it will grind the fibres of your carpet/furnishings/clothes. Good news: it's also a great deodorant.
Large objects like mattresses need steaming by a professional with a high volume, high pressure, superheating steamer. You obviously can't super-steam wood, and I don't know how they'd treat bed & furniture frames - burn them??
Bed bugs can walk far and fast (as can most lice!) They've been tracked marching miles, en masse, through wall cavities. crawl spaces, lofts and along or under roads. They're attracted by human pheromones and you can't stop giving those off while you're alive.
I mean, they deserve their place in the ecology (whatever the fuck that might be) but they're persistent little bastards. For thousands of years, bed bugs were just considered part of life. The only reason that ended was the invention of chemical insecticides ... and they've now developed immunity 😡