Heat. As Chewy pointed out. The Almond powder will melt with enough heat. He even suggested dissolving it in hot milk as part of prep.
The reason for it's popularity, I'd suggest , is simply because this dish recipe simply was not available online or in any book anywhere. Lots and lots of people wanted to know how to reproduce it but it just wasn't there to be found. It took me 20 years of searching before Chewytikka twigged as to what it was I was after. The rest, as they say, is now history. You'll see that I suggested a statue be made of CT for his contribution.
Obviously lots of Chefs in the IR industry knew what to do, but nobody else did. We do now. The rubbish dish in the jar by the P people is awful. There are recipes using green mango, mango chutneys and 1 even used mayonnaise. Hundreds of recipes for mango chicken exist, but they weren't the one. This is it. My daughters will attest it as they've endured 2 decades of failed attempts.
It still doesn't come up in a google search though.

Unless you include BIR in the search.