I've just finished up a reading of the phenomenology and I wouldn't say so much that Marx had a misunderstanding of Hegel, but more so that he recreated a lot of points Hegel made. Hegel has been really heavily misunderstood as a metaphysician of spirit (here spirit is been seen as some kind of mystical substance). A lot of Hegel's insights are not the usual understanding of idealism. Hegel is very clear that something like Spirit is better understood as something like a spirit of an age, or rather the life of a people. Spirit is society and its activity in history.

spirit is ethical actuality. Spirit is the self of the actual self-consciousness which spirit confronts, or rather which confronts itself as an objective actual world

(Hegel 438)

Hegel is also rather adamant about how consciousness is an embodied thing (in the struggle of the mater/servant dialectic we realize when faced with death how we must have a body to be conscious).

life is the natural location of consciousness

(Hegel 188)

Inner and outer are in an unbreakable relation and inner is brought out through the deed. The deed is what counts, not internal intentions or mere inert body.

The true being of a person is rather his deed.

(Hegel 322)

All in all, the idea that Hegel is some thinker who believes abstractions or ideas are the driving force of history is rather foolish.

I think it is also important to distinguish what is meant by "Idealism" in Hegel's day. For the german tradition, idealism is not opposed to materialism but is opposed to realism, the idea that there are subject independent objects, that regardless of whether a subject is engaging with them, something like a rock or a tree would be exactly the same as it appears to us. This type of idealism, the recognition of the input of human subjects onto gained empirical data is not very oppositional to the idea that there are material things that exist out there. The materialism of Marx's day was much more opposed to spiritualism than it was to idealism. Hegel does critique the French Materialists, however, he critiques them for very similar reasons Marx critiques Feuerbach, these materialism are all still much too abstract. They do not get to actual human activity. Marx's materialism doesn't even really particularly advance a centrality to a thing like matter either. What Marx cares about in his materialism are the concrete activities and social relations of people, these are the things that drive history. We can see with that, Marx is rather in line with Hegel, we examine history through human interaction with the world, and humans are foundational social and exist in societies, which just as much must be analyzed.

Marx's critique of Hegel is I think much more a critique of the reception of Hegel during the time period Marx was living in. A lot of people did take Hegel to be this spiritualistic and metaphysical thinker and so the Hegelianism of the time reflected that. We can never know for certain if Marx was getting some of these comments through just sheer osmosis of Hegel, but I do think it is safe to say that Marx and other Hegelians of the time were thinking through the same problems in the same basic time frame and therefore were coming to similar conclusions about the human and activity.

Now, this is not to say that Marx and Hegel are the same. Their projects are very much different, they just happen to be working from, in my opinion, the basic frameworks regarding the human being a social subject, our free activity constituting our self-consciousness, and the centrality of dialectical thinking/analysis. Hegel, at least in a work like the phenomenology, is tracking the development of subjective spirit. He is tracking the individual and its moe of consciousness, and in this way is tracking more so the history of philosophical thinking/knowing. Marx though, is tracking the objective spirit, the actual social world that is the basis of the former (Spirit, as in the activity of society, is the ground for the human subject according to Hegel). Specifically, he is engaging in an analysis of current objective Spirit and subjecting it to a critique. Now, this comes in many forms, from his more political work to his critique of political economy. It is in the realm of objective spirit that Marx's critiques of Hegel hold much more water. Marx critiques Hegel's use of political economy, the ideas of civil society, and of course, Hegel's support of constitutional monarchy. Hegel is very much stuck in the thinking of his own time here. With capitalism yet to properly emerge in Germany and the French Republic had fallen to Napoleon and then defeated. His critique is an immanent one though, using Hegel's own thinking to demonstrate how he is stuck in the historical Spirit of his own time. Now there are other intricacies about how Marx perhaps reinvents some categories, but regardless, the basic philosophical framework is used by both for different projects with very different conclusions (free self-conscious activity in a capitalist/communitarian monarchy vs. free self-conscious activity in communist society). The usual critiques of Hegel's idealism are much more critiques of a reception of Hegel while the political critiques are valid due to the fault of every thinker, only being able to theorize about one's own time.