Got me. Got me good.

When they signed their contract with Farian, they had no idea at all that they would be lip syncing. When they found out, Rob was pissed and confronted Farian, who threatened legal action against them if they didn't complete the contract. They weren't "in on it", they were coerced into going along with it.

They lied about the lip-syncing because doing so was a stipulation of the contract they signed with Frank Farian. The thing Rob and Fab were really guilty of is naivety. They were young and inexperienced and didn't read the fine print. Then, when Fab and Rob threatened to go public, Frank threw them under the bus and claimed he had nothing to do with it, despite the entire thing not only being his idea, but having long been his MO in the industry.

"They" are not pissed, because Rob is dead. I'm certain Fab is just thrilled to see people being successful because he's a super chill and legitimately talented dude who got screwed over.