Cubs underachieved this season. Not sure why you're struggling to understand that.
They didn't underachieve, they just had a bad September and lost a 5 game lead in final 20 games.
16-12 in September ..
Lost 4 of 6 to the Brewers ..
Losing a game to the lowly Reds and Whitesox ..
Ending the season at home against the Pirates and Cardinals and going 4-3..
Bullpen was a mess after losing Strop ..
Bats were very inconsistent ...
Brewers were insane, but 1 more win and that wouldn't of mattered
So. They didn't underachieve with 95 wins, they just didn't finish strong enough to hold off a red hot Brewers team