The two sentences have different meanings. These examples could help: a) He is now very well established in his area as a high-quality baker and sells a lot of cakes. b) He established his bakery business 10 years ago and it is now very successful. In a) "established" in an adjective meaning rooted, secure, permanent. In b) "established" is the simple past form of "to establish". The meaning is that he started, set up his business 10 years ago. The past participle is also "established".

In response to Andrew Wood's comment on my first answer; My example was present perfect and so I should maybe have picked an example which used the present perfect. But my simple past example is written correctly. "Ago" is used with the simple past not the present perfect. Also, "to establish" is a one-time activity and so would not often be used with the present perfect. An exception would be with "just or recently". e.g. "He has just established his business." The present perfect could also be used naturally with the the verb "to establish oneself" e.g. "She has established herself as a leading professional over some time".