I think the approach he took was too naive. I went to a meetup about "YouTube influencers" a few months ago who explained just this; there are companies whose sole purpose is to "vet" YouTubers and find you the right influencer for your product. They do all the heavy lifting for you, there's one pretty big one here locally called RoosterTeeth (yep they do influencer marketing nowadays amongst other stuff, if you watch h3h3 on YT they worked with him number of times).

The article was interesting nonethelss: the writer was transparent and laying down his assumptions and how they carried out the work AND the process. Executing a thing like this might be trivial but it requires a lot of annoying work, I know this by experience: even for simply sending a t-shirt to a customer (which is a simpler item is a pain).

Nowadays luckily you can send t-shirts or other apparel with a single click directly from the company that produces the item (there are a couple of names out there who will do that). BUT if you've got custom items or boxes of items (like in this scenario) you have to think about packaging, costs and the "unboxing experience", that last one is critical.

Unboxing experience can make or break the whole video.

I feel bad for the author who did so much work (180 attempts!?!) to get 17 videos and 0 sales and I suggest next time he goes to these specialists if he's really committed in using YT as a marketing chanenl.