Capitalism is based on growth which encourages mass consumption. Companies also use planned obsolescence (making a product so that it will become obsolete) to require consumers to consume more of their products.
. This results in the environment being unsustainably exploited. In The End of Growth Richard Heinberg argues that the global economy is approaching its growth limit since the environment is being damaged and depleted. 
Consumption is fundamental to capitalism and results in the use of limited resources, pollution, and the destruction of natural habitats which causes declining biodiversity. This end of growth can be seen in fossil fuel depletion. Resources currently being extracted are more expensive and difficult to access than in the past. 
Capitalism also ignores negative externalities (harmful consequences of consumption/production that is not factored into the price).
As a result, many corporations and businesses are willing to damage the environment in order to make a profit. It is more cost-effective for corporations to ignore their harmful emission levels or their contributions to pollution than it is for them to invest in environmentally friendly technology. In the end, damaging the environment is not only terrible for the earth and the species living on it, but it is also not cost-effective. The results of the climate crisis are having economic impacts that will continue to grow. In 2017, the US spent $306 billion on climate-related disasters. 
Unfortunately, capitalism focuses on short-term profits/costs. If an action is considered profitable then it is worth pursuing. This mindset results in capitalist societies avoiding environmental reforms that are needed to address the Climate Crisis. Investors who could possibly lose money due to their companies closing or being forced to adopt less harmful (yet more expensive) business practices have an incentive to spread false information and deny the existence of climate change in order to protect their financial interests.
Twenty fossil fuel companies are responsible for nearly "one-third of all greenhouse gas emissions in the modern era."
These companies continue to compete with each other to expand their businesses while ignoring their devastating impacts on the environment. Capitalism provides a financial incentive for them to do this that would not exist under a different economic system.