In Japan it can be different I think, even-though I've heard opposing statements on that I think. Nowadays (young) adults in other countries watch too because they grew-up watching on TV and so-on. Was Monster popular in other countries in the 2000s?
Monster didn't fall off a cliff as soon as its first half ended, I got more enjoyment out of the first 3-5 volumes of DN than the equivalent portion of Monsta tho.