It's incredibly easy if you control the narrative factories. For example, consider the sudden switch from "masks don't work unless they're N95, you need an MD to put one on correctly, and if you buy them you're an egotistical asshole who's putting our medical workers in danger" to "even plain cloth masks are useful, everyone must wear one at all times, and if you didn't buy one you're an egotistical asshole who's putting everyone in danger" earlier this year. Took less than a week.
I was pro-mask since before the narrative switch, but it would be completely irresponsible to sit back and say "oh well, good on them for correcting themselves, that's how science works after all". That was a real "we've always been at war with Eastasia" moment: a naked exercise of power, which could be used just as easily to switch from a true narrative to a false one, or from one lie to another.