Not all of them, but pretty much majority using wordpress. In ThemeForest theme devs making theme templates specifically for crypto/blockchain/ico sites. There is one example https://themeforest.net/item/icos-bitcoin-and-cryptocurrency-wordpress-theme/21626006 and I've seen quite a lot of similar sites with this theme, and there are much more themes.

As of making a website, it's pretty fast with WordPress, at least what majority do, buy the theme, install page builder, some plugins and you a ready to go. Usually to build fully functional page if you have all content, takes few days.