This is a dynamic we've not seen before - Zelensky is out and about so he's seen by his people, but a huge amount of this entire effort is being shared online through social media. You don't have to convince people its authentic - you can just convince everyone that everything is fake.
There's a subreddit called "AteTheOnion" which chronicles people mistaking wildly obviously fake and humorous articles from The Onion and other sites.
If people aren't able to discern those articles from reality what hope is there?
ISWYDT.
Same tactics as with what Internet at large nowdays calls "trolls". The onces that you spot were probably ment to be spotted, so you lower your guard against the actual propaganda that isn't as obvious.
I mean I like to think of myself as fairly critical and I do this. I'm sure there's a ton of subliminal messages that have established themselves as facts in my head.