Marxism was seen as liberation by many (but not all) ordinary people during the Industrial Revolution because it promised them the chance to retake their lives which were being dominated by their employers.
Marx argued that work in the capitalism system alienated people from their labor. It took away the fruits of their labor and gave it to others. Importantly, it also made it so that they no longer had control over their work and thereby made them hate that work. Because they now had to work when they were told and at the pace they were told (and because much of the value they created was taken by others) their lives were oppressive and unfree.
Marxism offered people a way out of this unpleasant situation. It promised them the opportunity to become their own bosses and to control their own lives. For this reason, many saw it as a liberating idea.