Hypothetical Question: Ring vs Tournament Player

[TheAcesRToxic]

If a given player is a winning cash game player, lets say 2+ BI's per 1k hands on avg, does that automatically mean they should have a high winrate in tournaments (MTT's/SnGs included). If not, why?

I often see many discussions about this person and that person being a tournament monster, but getting crushed in cash games and vice versa. Is there a reason for this? Comments from you guys would be greatly appreciated.