It's simply because he believes it. The leaders in Beijing believe that Taiwan should be part of China. We shouldn't underestimate that. We don't believe that, maybe, but that's what Chinese leaders believe. I think it's been effective as a point of unity with a very diverse and different kind of audience, the Chinese domestic audience. They are receptive to nationalism.
They're not alone. Many audiences domestically, like the Russians and maybe even the British, are receptive to nationalism. There's nothing unusual about that.