Why did the Big 4 become more famous than the other thrash bands?

[Thrash Til Deth]

While I would like answers to this question I will hopefully use this time to help broaden the thrash horizons of some people who think the big 4 are the only good ones here are some of my favorite thrash bands

Dark Angel
http://www.youtube.com/watch?v=GK6lc4BMGHI

Death Angel
http://www.youtube.com/watch?v=GK6lc4BMGHI

Testament
http://www.youtube.com/watch?v=dCYJXNLxSsA

Exodus
http://www.youtube.com/watch?v=T-PKAPDVsb0&feature=related

Venom (skip to 2 minutes in)
http://www.youtube.com/watch?v=_Sb46VD5CmA

Kreator
http://www.youtube.com/watch?v=ZbOFIkOYy6k

Sodom
http://www.youtube.com/watch?v=9V9WVz9yFt0

Metal Church
http://www.youtube.com/watch?v=1pultHqVOis

Sepultura
http://www.youtube.com/watch?v=hlVNC939T2w

Evile
http://www.youtube.com/watch?v=Hr9wObkGTYM&feature=related

There you go. Metal brothers enjoy it took me awhile to find all of these (and listen to em). Please nobody report me for ranting thank you