[Yo-Yo]

Can someone please explain in layman’s terms how the softest metal can strengthen the strongest one?

Easy. Here's the explanation from Science Magazine:

The fourfold increase in the hardness of Ti3Au compared to other Ti–Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation.

Child's play.

[Company Man]

and the pseudogap formation

Of course! I completely overlooked the pseudogaps! How foolish of me.

[Paradox]

Imagine, something as soft as Carbon can make Iron into Steel.