Please explain to me how MK beats Olimar?
I believe it's a slight advantage in MK's favor due to MK's defensive and punishing options being particularly nasty for Olimar.
The defensive side is similar to Brawl: MK has 6 jumps & a teleport to run away from Olimar for as long as he wants and N-Air removes any Pikmin that do attach. This is particularly notable on stages with high or off-stage platforms such as Smashville, T&C, Duck Hunt, Delfino, and Kongo. Time-outs shouldn't be uncommon in this MU.
An additional defensive perk to MK in this MU is that same 6 jumps + teleport on top of MK's increased Air-Speed compared to Brawl ensures MK never has to worry about Olimar Up-Smash unless he's recovering from ledge.
On the offensive side, MK has some of game's best tools for punishing whiffed moves and a very solid advantage-state but getting in does require Olimar to whiff something but, knowing Olimar's frame data, it's not particularly difficult; spacing and movement is key. When we do land a Dash Attack or Dash Grab, we combo then go for the juggle where Olimar's difficulty to land helps MK a lot.
MK also has the unique ability to kill all of the Pikmin in Olimar's line off an Up-Throw. Should Olimar ever get double Purples or a Blue when we're at throw KO range, we can remove them from play. Olimar does have time to pluck more Pikmin while we're killing them if he's very quick about it and doesn't hesitate but he gets knock-backed back too far to save his old Pikmin.
Additionally, Olimar's recovery is real bad in this MU. At 80-90%, MK B-Air flat-out KOs Olimar off-stage.
The reasons this MU is still close from the Olimar side are Olimar's superior spacing and zoning tools, purple priority, KO throws with Blue Pikmin, and his styling space suit. Olimar dominates the pace of the match as he can advance his defensive wall and push MK to the ledge or into the air where is punish game in the weakest. He also forces a reaction with Pikmin Toss which tells MK where he is and is not allowed to be on the ground.
If Olimar plays safe, so will MK. If Olimar plays aggressively, so will MK. That's what I mean by Olimar dominating the pace. If an MK doesn't respect that, he will lose. But if that MK plays Olimar's game, they'll find that Olimar
needs MK to run into his moves to get much going and that's where MK's defensive tools shine through; MK's great at approaching most characters but, in MUs that call for it, he's great at running away as well and punishing attempts to chase him.
Olimar wins so long as he perfectly boxes MK out but the MU shifts far too hard in MK's favor when he sneaks in a move and gets stage control to call it even; Olimar's punishes are nowhere near as severe as MK's and I'll happily trade getting hit 3 times before getting one Dash Attack because MK can make-up that damage and more with stage control. But again, overall, I think it's a
slight advantage towards MK.
All that said, the only Olimar I have tournament experience with are Freebeast and Nom but I'm sure not many other Olimar have solid MK experience either.