(I'm probably some ways wrong about this in my lingering naivety [and, so, happy (eager, even) to hear counter-arguments, refutations, educations otherwise], but...)

I see Engels as part responsible for leading Marx astray from listening to Bakunin['s warning] [1].

It's my impression that younger Marx was much more fervently libertarian along with his economics, and then later stripped the freedom to a mere wishful happenstance footnote in preference for a more purely economics focus, which opened the door to the authoritarians to usurp his work, and turn it into the whole "well then we'll make them free" and "some are more equal than others" cognitively dissonant perversion.

[1: quintessentially: "We are convinced that liberty without socialism is privilege, injustice; and that socialism without liberty is slavery and brutality," -- Mikhail Bakunin]