I think the real thing that made it go viral are the "certificates" it gives you for solutions, which get shared on social media:

https://www.kaggle.com/benhamner/wordle-1-6

While that is a part of it, I have also heard that the virality was somewhat forced by journalists writing about wordle endlessly: as fans of word games themselves, journalists boosted its popularity in the earlier days, driving a lot of the 'viral' traffic.

Can somebody tell me how to generate one of these certificates? I can't find a button on the page at all to do it and I feel like a moron, since everyone and their dog is posting them on Twitter.

When it pops up the results dialog after you win, there's a green "Share" button in the bottom right. If you closed the results dialog, you can get it to open again by refreshing the page.

You can also just click the bar graph icon in the top right, next to the settings gear.

After successfully solving the daily puzzle, you're presented with a small popup that includes stats and a share button. The share button adds the sequence of emojis to your clipboard.

In the dialog that shows up after you finish Wordle, click the big green Share button and it's copied to your clipboard

Press the graph icon next to the "WORDLE" on the top of the screen, then press "share"

If you have an ad blocker on it won’t show

Well, there's no timer in wordle whereas in lingo you are against the clock. You only get to play one puzzle a day.The solution is the same for the whole world every day.

Part of its success is the simplicity I think, and the fact you don't need an app.