I suspect the primary motivation for funding ethical AI work is _public relations_ (or less kindly, corporate propaganda) - to help mitigate damage to Google's brands and reputation by public concern surrounding artificial intelligence.
It is well understood that it can be difficult to get someone to understand something when their paycheck depends upon them not understanding it. Conversely, it may be difficult to remain employed and continue drawing that paycheck if you publish research that does not portray your employer in a good light, especially if the underlying reason for your role is public relations.
Here's a fun experiment: open up Alphabet's annual report from last year [goog10-k2019], search for the keyword "ethic", and there are two hits, both under item 1A, risk factors. The latter keyword match for "ethic" in the 10-K is regarding supply chain risks, and the potential for unethical behaviour by alphabet's suppliers. But the former keyword match is far more interesting:
> Our ongoing investment in new businesses, products, services, and technologies is inherently risky, and could disrupt our current operations and harm our financial condition and operating results.
[...]
> In addition, new and evolving products and services, including those that use artificial intelligence and machine learning, raise ethical, technological, legal, regulatory, and other challenges, which may negatively affect our brands and demand for our products and services. Because all of these new ventures are inherently risky, no assurance can be given that such strategies and offerings will be successful and will not harm our reputation, financial condition, and operating results.
[goog10-k2019] https://www.sec.gov/Archives/edgar/data/1652044/000165204420...