Put into bat on Sunday evening, KKR never got going on a slow, sluggish Wankhede and managed to post just 133/7 in their stipulated quota of 20 overs.
Robin Uthappa played an uncharacteristic knock of 40 from 47 balls, scoring 25 dot balls on a day when KKR magic wand Andre Russell failed to deliver.
The big-hitting West Indian walked out to bat at number 5 after Mumbai had built up the pressure on the visitors. Russell fell to Lasith Malinga for a duck and KKR, from there on, never managed to push the accelerator.
Mumbai chased down the target with ease, riding on unbeaten knocks from skipper Rohit Sharma (55) and Suryakumar Yadav (46) to seal the top spot.
After the match, KKR skipper Dinesh Karthik rued the fact that their batting didn't come to their own in a must-win game against Mumbai.
"We didn't find momentum after the 6-over mark while batting and the regular wickets didn't help either. We simply didn't get going," Karthik said in the post-match presentation ceremony.
He also defended the decision to hold back Russell, saying, "There was an opportunity to bat up the order for Andre Russell, but expecting him to deliver every time is unfair and he has been fantastic throughout the tournament for us."
The KKR skipper, however, assured fans that the team will come out with a much-improved performance in the next season.
"Not our best season, there are a lot of areas for us to improve on, and I'm sure we will come back stronger next year," he said.