Well for one there is lagless landing cancelling for many moves. I think every character's neutral air and Z-air (if they have the latter) automatically cancel all lag on the ground when you land while using them. Essentially it is Z-canceling in 64, only without clicking Z (thus being automatic).
On top of that, ground moves combo into each other really easily. The ground game feels A LOT like Smash 64.
This all leads to easy followups, especially since there is a lot of hitstun. The hitstun is actually overall pretty strong, and allows you to follow up an aerial attack with just about any ground attack that you can launch in 20 frames, including essentially every smash attacks.
Characters get KO'd easier too, as they get KO'd at lower percentages. If you don't abuse a move (thanks to stale move negations, which is a much bigger deal than in Brawl, especially with the high roofs), you can often follow up aerials (or up tilts, a lot of which combo into aerials [which aerials combo into ground moves; see a flow=???]).
For one combo with Toon Link on Marth, I was able to use all this knowledge.
My boomerang on the return landed, and I followed up with a forward air (normally a KO move but this was low percentage) into a lagless landing into an up tilt, another up tilt, and a last up tilt into a lagless Z-air into a forward smash (I got both hits of it) for a KO and a combo that did about 40% easily.
I could have likely extended the KO.
But yeah, with all that extended hitstun, the lagless landing, ground moves being combo machines, KO moves doing a ton of knockback if you don't have stale moves negation, and the lack of sideways DI (watch footage MvC3; that's what the DI feels like [minus the ability to jump THAT HIGH THAT EASILY], and it makes it hard to defend in the air, especially since hitstun prevents air dodge spamming defense and air dodges aren't as good) all add up to a more offensive game with more combos and KO's.
Hopefully that answered your question!!!