If you draw a line with two curves in the sand in front of it, you can mesmerise a chicken or chickens..
as a politician once said to another when I lived in Malta.."the honourable member has the mind of a chicken".
There are a lot of people with the minds of a chicken, youtube and twitter and facebook and other "social media" tends to attract them ( actually such sites are designed to attract them, because in addition to having the minds of chickens, they are "click happy" and have disposable income, adsense works on the same principle, as do adwords, and in fact most advertising ) .

However, far fewer purchase than follow ( in most niches, an exception being such as Kylie Jenner and her cosmetics empire )

most advertisers ( rightly so ) suspect this to be true ) but as the social media sites ( and Google ) "black box " their figures ( black box being an industry term for lying about )..advertisers keep buying the ads, because..

1) They are terrified that if they stop, the competitors will get more clicks, eyeballs and sell more ( this "fear" is encouraged by Google and the "social media", such "fear" is good for the "bottom line", and the quarterly profits )..
2 ) Businesses get to write of advertising costs against tax..
3 ) Eventually the cost of all those ads, gets passed on as increased prices anyway.
4 ) As I have said here previously, if people knew how advertising ( and "viral" ) worked , that is to say what parts of the psychology are being affected, and why , they would deny that they were affected, deny that they could be affected, would not even be willing to admit to themselves that the(ir ) "lizard brain" was being affected..

posted with the knowledge gained and used from 10 years working in advertising..
and also the knowledge that those of us who know the hows and why of how such things work, are not supposed to talk about it..

a 2-minute silent video of a lemon rolling down a hill

It's not silent. The lemon makes sound rolling and the cameraman's feet can be heard walking.

How can a tweet from a small account get in front of enough eyeballs to get the initial traction?

It takes several users with large follower numbers to champion the tweet, or video. Just a couple of the right people is almost all it takes.

I have about 50k Twitter followers and every so often one of my tweets achieves viral status (>100k retweets) and when I look, my tweet was only retweeted several hundred times by my followers, but the next layer of retweets went crazy.

BTW - I was working on a rolling orange video. Guess I'll scrap that idea now.

Whoops - looks like I lost a few followers due to Twitter's housecleaning [webmasterworld.com]

Try making a video about an orange that rolls uphill..or an apple..but a softcore one.

It takes several users with large follower numbers to champion the tweet, or video. Just a couple of the right people is almost all it takes.

That's an interesting perspective. Have you tried to analyse your viral tweets to pin down the exact people on the next layer who made your tweet viral? And then engineer virality next time around by "engaging" those specific people?

I think these were the chaps who made the Lemon video viral but I found out about it too late to be 100% sure of my analysis. @jonnysun & @tedleo

or an apple..but a softcore one.

Or a video of an apple that gets squashed between two PCs... oh no, oh no, I've just managed to alienate 90% of WebmasterWorld users :(

Have you tried to analyse your viral tweets to pin down the exact people on the next layer who made your tweet viral?

I haven't. I don't really spend much time or effort on Twitter.

Despite the 50k followers, I don't follow anyone and rarely read anything. I just load up a scripted flatfile with tweets each morning and forget about it.