I think everyone putting their name to a professional opinion projects Sergachev with significantly higher offensive upside.
Trouba himself has more offensive upside than Trouba if he's put into a perfect situation.
You are saying Sergachev projects to be more than a 25-30 pt dman, which is probably true. Although easier said than done...
If Trouba played with Enstrom 5v5 and played instead of Buff on the PP than he'd have more points. Maybe one day Sergachev is a 25 pt dman because there is a better option on his team for PP, and he is the best PK guy the team has. Won't make him worse of a player. It's about how he is utilized within the team.
There isn't anything Sergachev has done yet that warrants any more hype than Trouba had after his first year at Michigan and WJC performance.
Not a good trade for the Habs, I agree.