The short of it is after collapse of Communist Party of Burma a lot of those EAOs formed in the wake. Kokang was one such under control by a group called Myanmar National Democratic Alliance Army.
In 2009 the Burmese (pre-junta) government troops attacked MNDAA and the 2nd in command in MNDAA defected to the government side. A new local government was formed and Burmese government troops were stationed in Kokang. MNDAA remnants retreated deep into the mountains to hide.
Neither MNDAA prior to 2009 nor the subsequent government were pleasant people from PRC point of view. MNDAA Kokang's economy was mainly drug trade (80% of it going to China) and post 2009 Kokang's economy shifted to scamming.
Recently MNDAA re-emerged and is attacking what they see as collaborationist and traitors with government troops, using the whole anti-scam thing as their reasoning (and with suspicious amount of Chinese origin heavy weapons). They are making a lot of progress. As far as we can tell their years hiding away in the mountains has lead to some reforms in MNDAA. They have swear off the drug trade and their troops seem highly motivated.
But still, Chinese people shouldn't project themselves into any of these groups. Just look at the response from Wa State the most powerful and most pro-China of the EAOs:
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Wa State is calling for ceasefire from both sides, not taking either side, accepting any refugees fleeing Kokang into Wa State and will attack any troops entering their territory.
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This is MNDAA calling for "collaborationist forces" to either lay down their arms or rise up and join them to kick out the government troops. They nailed down that Chinese Civil War feel with the language.
