"The Cubs will do anything to prevent themselves from breaking that streak of not
winning a World Series since 1908."
This move was made to try to keep some fans watching. Go look at the Cubs payroll and compare it to years past. I am not a fan of Jackson, but this move for them made some sense. It's a 4 year deal, they don't have to give up a pick(which they value highly at this point in the rebuild btw), and he compares favorably with Anibal Sanchez who the Cubs were in on.
Jackson is 26-22 with a 3.80 ERA and 1.31 WHIP in his last 75 starts and signed a 4 year 52 million deal. Anibal Sanchez is 22-28 with a 3.79 ERA and 1.28 WHIP in his last 75 starts and signed a 5 year 80 million deal.
So in the end, the Cubs might have overpaid in terms of dollars and years, but they have more than enough money to do so and needed some kind of rotation help. Would I like to see them continue these type of signings? No. But I can certainly see why a team in that situation making a move like this.