I wonder as well how they exactly achieved this, but my technical understanding is to limited. You can read the new whitepaper of the coordicide to evaluate their approach.
But from what I heard about IOTA and how they communicate with the public they seem to be pretty confident that they are about to solve this problem. They have a lot of brilliant minds working for their foundation and a lot of scientific research went into this project. I'm hoping that someone can explain this in Lehman terms.