First, the response was to a comment that said the Twins had Lewis and Lee cued up to play - and that was not true.
Second, the Twins made the play-offs (and Correa was arguably their best position player in them), so it certainly wasn't a 'mistake' last year - it's possible the Twins don't beat Toronto if Correa wasn't playing shortstop for them.
If Correa returns to form next year, it certainly won't be a mistake. The planter fasciitis that plagued him last year wasn't even remotely related to the past ankle injury concern expressed by the two other teams (neither of whom made the play-offs, BTW).
I don't know anything about Correa as a person - my analysis is based on the Twins results last year, and his career to date. The guy has put up 40.9 WAR in the equivalent of about 8 years in MLB, he's won a Gold Glove, been a three-time All Star, Rookie of the Year, and will be entering his age 30 season. To claim the signing was a 'mistake' based on one sub-par year strikes me as based on entirely insufficient evidence.