So, first we must define what capitalism is. In the simplest terms, capitalism is a mode or a system of production, i.e. the way in which the production of commodities is organised within society.

The kind of capitalism as Adam Smith describes it originated with the 'Enclosures' in England. These precise length of this period of enclosures is debated, but we'll go with 1700-1850. These enclosures were a very complicated period that I'll try to explain below, and also the period that gave rise to capitalism.

So, starting with a feudalist mode of production, land ownership was organised as follows. All (arable) land was owned by the lords, who in turn 'owned' serfs to work the land. These serfs would produce x amount of food and other raw materials, a cut of which went to the lord, generally leaving the serf with enough produce to feed himself and his family. The lord took from his part what he needed to feed himself and his family, and anything that was still left he sold in the market (the 'surplus', in economic terms). The important thing to note here is that the serf did not sell his labour. Also, there was no real estate market, land was not being bought and sold. You either had land because you were a lord, or you didn't because you weren't. The only way of getting land you didn't have was by conquest, political games or by because the king have it to you as payment for services.

In this feudalist mode of production, the order of the components of the production process are important to remember. First, there was production itself, the serf cultivated a crop. Then, there came distribution - the lord took his share. Finally, there was 'the market', so at the end of this process, debt and credit appeared. The order is therefore: production - distribution - finance, market, credit, whatever you want to call it.

Beginning in the 16th nd 17th centuries, however, things began to change. Technological improvement, state consolidation and navigational discoveries created something like a pre-modern global market for commodities. This allowed merchants from England, Holland, Portugal and so on, to make absolutely tons of money by, for example, buying spices for next to nothing in the East and selling them for loads of money in Europe, while selling European wool to the Indians, for example. This process of capital accumulation, however, caused a major social change in European societies. Previously, the aristocracy had complete political power, military power, and consequently, economic power. They owned the land, they received the surplus, and thus they solely controlled finance. The political and economic sphere of power were therefore one and the same.

These merchants, however, started earning an amount of money grossly disproportional to their social status. They had no political power, but they very quickly gained economic power. The spheres of power began to separate, with economic power gradually shifting to the merchant class/bourgeoisie, even though they did not own land. This is the emergence of the capitalist class. So, to answer your question, the aristocracy could not reinstate feudalism because the economic sphere of power shifted away from them.

However, because wool now had an exchange value on the global market, land, too, gained a potential exchange value because it became required in the production of international commodities. This is when the enclosures start: the lord, eager to get in on this international trade business, realised that he was wasting his land by having serfs on it cultivating beetroot and whatnot (that had no value on the global market), when he could have sheep on it that produced wool which he could then sell and make a big fat profit in the process. So, with the help of the king's armies, the lord chucked the serfs off the land, built a fence around it, and sets out getting himself some sheep. So, land gained and exchange value determined by the price of wool on the international market, and 'common rights' to land were abolished.

Simultaneously, the labour market is born. The serfs, now without a means of subsistence, started knocking on doors asking for work in exchange for money to feed themselves. Labour, then, became commodified because the serf now lacked access to the means of production, i.e. land. Luckily, there as some work around - the lord needed people to look after his sheep. So he hired the serf back to his land, but now, the serf was forced to sell his labour rather than 'inherit' land and his position by customary rights.

Remember the feudal order of production (production - distribution - debt/credit)? This now reversed. The lord invited the serfs back onto his land, not as serfs, but as small-scale entrepreneurs who rented his land from him (the lord refused to do any work himself). These involuntary entrepreneurs, in turn, hired other landless serfs. So, whereas finance had been the last step under feudalism, it became the first step under this new (proto-)capitalist system. Before any wool had been sold, the serf had to pay rent to the lord, and wages to his employees. The entrepreneurial ex-serf, of course, lacked the money to do so. So, he went into debt.

Because debt and credit now became the first step, the potential revenues the entrepreneur stood to earn from 'his' business were already largely distributed. In fact, this is where surplus value comes in. Once all these costs had been paid, whatever was left at the end of the month went to the entrepreneur. This is the essence of capitalist production - the capitalist gets the surplus value. But if the market for wool collapses, he is also the one to lose out (unless he fires his employees, like we still see in modern capitalism today). So, distribution came second, and the actual production of the wool came last. The primary factor was debt, then distribution, and finally production.

And in this way, capitalism emerged. The entrepreneur was now in direct competition with all other entrepreneurs who had also rented land. This process also created all the other forces we associate with capitalism. The entrepreneur now had ample incentive to try and reduce costs, i.e. increase his surplus value. So, he tried to reduce costs by cutting wages, and/or he went into even more debt to invest in technology that would give him and edge over the rest/keep him in business. In short, profit maximisation occurred. This created unimaginable mountains of wealth for a few people, but at the same time, it created a stupendous amount of debt, also for the entrepreneurs now part of a rat race for survival, inequality and general misery for the have-nots.

Of course, the questions of how capitalism came about has a wide range of answers, depending on one's academic tradition and so forth. The answer I gave here is primary built on the post-Keynesian and Marxian schools of thought regarding economic history. Specifically, the works of Yanis Varoufakis, Richard D. Wolff, Karl Marx, James K. Galbraith, John Maynard Keynes and Paul Sweezy.