Lucario has no verticle DI and he dies earliest from verticle KOs. Because he needs to be able to survive before he can make use of aura, and we all know Snake's UpTilt KOs so early, he can hardly be considered a counter or even. Just look at what Ally did to Azen. It wasn't too pretty.
There's a lot more to the match up then that:
1. When done right, Lucario has a 0-40% chain grab on Snake using the force palm.
2. The aura spheres stop grenades, greatly deter the path of nikitias, and "dip" low enough to blow up mines.
3. Lucario's Aura Sphere is one of the few attacks that can directly destroy the cypher if aim right like Wario's chomp and Mario's fair.
4. Utilt easily juggles Snake.
5. Dair can cancel out mortars if timed right.
6. One of Snake's biggest weaknesses is dealing with projectile spam and Lucario's are second in this match up probably only to Falco's lazer and Pit's arrows. (side note: I believe the Pit/Snake match up is about 60-40 in Snake's favor. The arrows are one of the few things that keep this match up from being an absolute suck-fest.)
7. Fsmash is probably one of the safest smash attacks in the game if spaced right and one of the few that can be reasonably spammed. It outranges Snake's ftilt and can easily stop mortar slides.
8. Snake's high damaging attacks make Lucario more formidiable faster and make previously mentioned attacks more effective.
9. Snake's slow aerial velocity make it easier for him to get stuck in strings of fairs. Dthrow into fairs work especially well against Snake.
10. Most of Lucario's attacks have disjointed hit boxes which allow him to space himself better than most characters against Snake.
This is a match up basically based on paitence. Lucario doesn't have many options upclose(especially with dsmash and usmash being garbage) so he mainly suffers if Snake gets in his face and is very aggresive (Ally is exactly this). Granted, Lucario can do jabs/force palm/utilt/grabs upclose but he suffers if he sticks around for too long like Wario against King Dedede and Olimar against Metaknight. If the Snake is campy and defensive, then the match up is in Lucario's favor because he can deal with it better than most characters. In the end, Lucario vs Snake is about even based on each player basically having an advantage if Snake is aggressive or if Lucario is defensive so it pretty much evens out.
Add in:
Come to think of it, the King Dedede vs Snake match up is a lot like this too except Snake wins out if he's really defensive and King Dedede wins out if he's really aggresive.