The liberal revolutions of the centuries before that were all about taking power away from the (monarchical/aristocratic) government in order to establish a society in which the government was elected by, and served, the people, and there were no longer any formally defined classes and all inequalities that remained were about income and property, which were (at least ideally) possible to overcome through one’s own achievements… why did communists ever think that the next step after that might be to once again establish a powerful government that serves as the only (or only major) employer, that’s a movement precisely in the other direction, not the natural next step…

Because the liberal system leads to concentration of wealth and allows for outsized political influence by the rich (which leads to wealth becoming even more concentrated). The rich also have significant influence over people’s lives as employers, outside of the political sphere, and they are accountable to no one. The fact that “ideally,” on an individual level, anyone could hit it big does nothing to address those systemic problems.

The state, as an employer, is more accountable to the people than a private individual or company is, because it has to answer to the voters. Naturally, that also depends on taking measures to prevent the bourgeoisie from exerting their outsized control on said state.

There are advantages to having private companies and competition, but those advantages tend to disappear as the economy becomes more developed and saturated, and the tendency of the rate of profit to decline kicks in. Once companies can’t increase profits by expanding in productive ways, all they do is enshittify their products and look for new and innovative ways to fleece their customers. In such cases, the profit motive causes more harm than good, and the industry would be better off run by the state.