Yeah, it definitely comes across as a perjury trap. What Cohen admitted he lied about under oath, was that plans for Trump tower in Moscow didn't end January 2016, but rather June 2016 further into his presidential campaign. That's it.
The business meeting in general isn't actually illegal, but the lying to cover it up so hard and avoid the bad pr is. And that is what they got Cohen on here and may get Trump with with his written under oath answers.
I do admit it raises the question of why lie so hard to hide a legal thing? Was it just because of narcissism and thinking they could do whatever they wanted and not get caught? Or is it more?