Archbishop Lefebvre was clearly in compromise mode in the early 1980s.
That is quite open for debate.
First of all, define "compromise" in this specific context. What exactly are you accusing +ABL of? Let's define our terms.
Your own hardline/sedevacantist stance has colored your view of the rather distant past -- 30 or 40 years is a good chunk of time, in terms of human lifespan.
Treating with the Pope, we're talking about the Vicar of Christ here, when no one had been betrayed yet, is not compromise. "Someone had to try". Afterwards, YES, you should know better. We have since sounded the depths of the Crisis in the past several decades, and now any person with their eyes open is blackpilled about the Modernists and the state of the Conciliar Church in Rome. Most sane men today think only God is going to be able to sort it out. But that was not the situation in 1983. The Crisis was still young!
Going back to see if any of your house is still there, in the days following a massive wildfire, isn't crazy.
Going back 40 years later, long after the wildfire burned the entire town and it's common knowledge -- THAT would be crazy.
+ABL did the former, Bp. Fellay did the latter. There is no comparison in the actions of the two men.
Action X done in 1983 might not be compromise, whereas the same action X done in 2012 would be the most craven and cowardly of compromises. It's all about the circuмstances.
Just like packing up the family and moving 1,000 miles could be the peak of wisdom and prudence for one family, but the height of folly for another family. The CIRcuмSTANCES define whether an action was prudent or foolish, and a wise action or a craven, foolish "compromise" with error/evil.