Let's just say, given the number of harmful and non-environmentally friendly industries that were in China, if investors brought harmful industries there, they did not affect the overall, already formed picture of environmental pollution.
But what exactly the investors brought was TECHNOLOGIES. Due to which China has become what it is now! Without technology, China would still be a third world country with bleak prospects ...
Being a regular visitor to India, I always compare China to India. You can also compare China to some of the other more populous Asian nations, such as Indonesia or Pakistan. None of these countries have witnessed the same level of economic growth as China. And regarding India, I would say that they wasted a perfect opportunity. If the corruption, bureaucracy and red tape was not there, then India would have emerged as the most preferred destination instead of China. They had the perfect conditions, such as large English speaking population, low wages, and moderate climate.
China attracted investment, because they could do away with the regulations and make it easier for the investors to set up factories. As you have mentioned, these investors brought new technology, and this enabled ordinary Chinese to setup worldclass technological startups.