Genuine question, what inside info did he have?

Also

"Initial drummer Carruthers was replaced after Mustaine and Ellefson decided they could not trust him. Carruthers had chosen to hide his black heritage from them by claiming he was Spanish, and they could not understand why he would deceive them.Brett Frederickson joined the band in November 1983 as their next drummer."

That move probably hasn't aged well. Pretty nasty.

Edit: I can't recall which podcast I heard this, but ismtbhebthe guy that was sad that his band didn't sell as many records as Metallica?

Completely unrelated to the article claims.