In other words, the answer is that clouds move because the wind blows.
However, wind does not refer to the wind blowing over the ground, but to the wind blowing very high in the sky. Even when there is no wind at all on the ground, there can be strong winds in the sky. It may seem strange to see only clouds moving when there is no wind around us, but clouds are moving in the sky, driven by the wind.
However, there are some clouds that hardly move even when the wind blows. This is the case with clouds created by the topography of high mountains such as Mt. Fuji. These clouds are called "kasa" or "tsurushi" clouds, and they hardly move even when strong winds blow in the mountains. These clouds look like berets on the tops of mountains, so please observe them carefully when you see high mountains.