To understand this, we need to understand the difference between the claim that Bengal had a prosperous manufacturing sector, and the claim that they were "show[ing] signs of industrialisation," or that Bengal "was going to industrialise."

The first is an uncontroversial claim that Bengal had a substantial manufacturing sector. Artisanal cottons and silks were produced in large volumes, and were famously traded internationally as one of the great luxury goods. There was also a substantial shipbuilding industry, as well as gunpowder manufacture. In some ways, this mix of industries is not so dissimilar to the Netherlands, or to England itself, in the 17th century, or indeed the urban economies of the mid-Song dynasty in China at its peak. And it meant that the urban areas of Bengal were relatively prosperous, at least until the disasters of the mid-18th century, culminating in the EIC takeover. By the standards of the early modern period, this was a major centre of manufacturing and trade. But then, so was the Netherlands, and a hundred years after the beginning of the industrial revolution, they had fallen well behind Britain, Germany, and France. Pre-modern prosperity does not necessarily imply imminent industrialisation.

What is unclear is how Bengali artisanal manufacturing would lead to industrialisation in the sense of a one-way transformation of the economy away from subsistence and into persistent growth driven by technological change. Textiles manufacturing and (wooden) shipbuilding are skilled crafts, but they do not lead to the replacement of human and animal power with machine power fuelled by combustion, which was the genuinely revolutionary part of the industrial revolution. Had Britain only invented spinning jennies and flying shuttles and so on, it might have led to an export boom in textiles, but it wouldn't have led to a fundamental lifting of pre-modern constraints. The real transformation was the application of fossil fuels (coal, most prominently), the invention of the steam engine, blast furnaces for producing iron and eventually steel, and the beginnings of mass production rather than artisanal production.

The origins of this change in Britain are still debated, but the two prevailing theories are Allen's factor prices argument: that labour was expensive and capital was cheap, which incentivised the invention, and more importantly adoption, of machinery, and Mokyr's culture of growth argument, that the seeds of technological change are found in the slow but profound diffusion of scientific ideas, and the social structures necessary to apply those ideas to the problems of production. Bengali skilled artisans were skilled and well-compensated, but wages for ordinary workers were generally quite low, especially outside the cities, and the cost of capital was quite high. There was little incentive to innovate labour-saving methods that involved complex machinery, as workers were relatively cheap, and machines were expensive.

The culture of science and technology arguments are more ambiguous. I would be interested to read a good work on the state of the Bengali culture of science and technology during the Mughal period, and I am sympathetic to the argument that existing arguments about "why not India" from the European side have been more dismissive than detailed. But I am unaware of any argument that Bengal was integrated into a flourishing web of scientific research and dissemination of knowledge in the way Britain clearly was by the 17th century. Bengali artisans certainly possessed plenty of knowledge of both the technical and artistic parts of their trades, to the point where their methods and aesthetics were widely copied. But the overall mechanisation was at a sophisticated but still pre-industrial revolution level even in textiles.

There doesn't seem to be much evidence of emerging development in other areas. We do not know all the contributing components as to why these things occurred in Britain, but we have some fair guesses; very few of these likely prerequisites can be found in Bengal, despite its prosperous artisanal manufacturing sector. Bengal has exploitable coal deposits, but they were not used until the colonial period. Perhaps they were not necessary, but neither could they play any immediate part in a supposed incipient industrial revolution (but for colonial rule). A Bengali industrial revolution would have required much more than just higher incomes and innovations in the handicrafts sector. It would have required steam engines, blast furnaces, railroads, and factories. And to create those things, it likely would have required agricultural innovations to sustain ever-increasing urbanisation; the educational, scientific and technological resources to generate a constant flow of improvements and inventions both at the practical and theoretical level; a state able to impose both internal and external stability and yet mostly refrain from excessive appropriation or taxation of any early economic successes. (Or perhaps, in deference to the colonial plunder argument, to do the excessive appropriation and taxation halfway around the world instead of at home. I don't think this was the critical factor, but if one thinks it was, then it is not very clear how Bengal would have replicated it.)