You, the regime, can will things out of and even into existence with a few clicks.
Sort of. It's not like this information doesn't make its way into China and it's also not like the millions of people who remember him existing all died. So it's more like you can prevent people talking about it in public.
Plenty of Chinese people still talk about the Tiananmen Square Massacre. They're just not allowed to do so. They do it anyway.
So they can hide it from public discussion, but they can't hide it.