Kyokushin Kumite

Why Kyokushin kumite looks very different than other style of Karate? it's close to the Thai boxing.

Well, its there take on karate. It was Oyama's vision to some extent (though he wanted face punches). I'm not a big fan, it seems to promote the stronger tank types and I rather be of the mobile and precise attacks class myself.

I do not fully understand your question. What are you asking specifically?

Kyokushin kumite is full contact and has other rules and other goals. The rules and goals are actually more similar to thai boxing than karate point sparring.

The main difference between muay thai and kyokushin kumite is that muay thai allows punches and elbow strikes to the head (but kyokushin does not, both how ever allow kicks and knees to the head) and muay thai allows clinching.

The main difference between between kyokushin kumite and karate point sparring is that kyokushin allows low kick (not to the knees though), it is full contact, it does not award points for single techniques unless they down the opponent (it depends though, there are various rules in various tournaments and also different rules for juniors).
Matches are often won by decision of judges.

Just to add to that for FYI, there are other derivatives of Kyokushin which allow throws, holds, sweeps, and submissions. Enshin, Ashihara, Daido Juku, Byakuren and a few others but those are so far the most popular variations of Kyokushin. Daido Juku is the only one to allow headbutts; along with everything else. Check them out on youtube. These are also known as knockdown or knockout styles of full-contact fighting. The judges play a part when the winner cannot be determined by skill and if neither of the knockdown/knockout aspects presents itself. And if that cannot be determined after two extended rounds then a weigh-in occurs to help determine the winner. All of this is dependent on the rules of that particular tournament.

Similar to boxing, judo and many other forms of sparring, in kyokushin bigger and heavier fighters have a considerable advantage over smaller and lighter fighters.
And like in judo and boxing, lighter and smaller fighters in kyokushin tend to be faster, more agile and more mobile and it is much more exciting to watch light weight fights than heavy weight fights (IMO) even though the heavy weights are considered to be some kind of elite.

Please don't judge kyokushin kumite (or other styles for that matter) too quickly even though you wasn't impressed by your first impression (I think it is common that karatekas from other styles don't get a good first impression of kyokushin).
I think all of us have some kind of tendency to think that our own style is the best and superior to other styles, but if we keep our eyes (and mind) open, we are more likely to see the beauty in other styles, and we all like seeing beauty don't we?

Similar to boxing, judo and many other forms of sparring, in kyokushin bigger and heavier fighters have a considerable advantage over smaller and lighter fighters.
And like in judo and boxing, lighter and smaller fighters in kyokushin tend to be faster, more agile and more mobile and it is much more exciting to watch light weight fights than heavy weight fights (IMO) even though the heavy weights are considered to be some kind of elite.

Please don't judge kyokushin kumite (or other styles for that matter) too quickly even though you wasn't impressed by your first impression (I think it is common that karatekas from other styles don't get a good first impression of kyokushin).
I think all of us have some kind of tendency to think that our own style is the best and superior to other styles, but if we keep our eyes (and mind) open, we are more likely to see the beauty in other styles, and we all like seeing beauty don't we?

Couldn't agree more. Most make comments based on youtube vids and think they know all there is about what they saw and not what they experienced, such as the first kyokushin class. Whole different world when you actually witness what is involved to achieve those attributes in those videos!