Like most questions regarding big events in this sub, you can find comprehensive answers previously provided.
Some good responses in there, happy reading.
/u/krishnaperkins has a good writeup, and another user lists other related q&a again from this sub.
In summary, it's not an apples for apples comparison. The mongols were brilliantly led both strategically and tactically, their army had more mobile supply, kievan rus was smaller geographically and population wise vs the later Russian empire and successor state USSR, amongst other factors.
I just got a notification that someone replied to this, but Reddit is dumb and won't let me see it-not even in messages. So, whoever replied that, two things:
1: Maybe try commenting again so I can see it this time?
2: By "everyone else", I primarily meant Sweden in the Great Northern War, France in the Napoleonic Wars, and Germany in the World Wars and am aware that there were several other invasions, but I've heard the Mongol invasion be referred to as the successful one. Were there any other successful invasions?