You don't 'trust' them. You look at the results they present and evaluate their degree of bias on that particular topic. Depending on what and how you search, their results are usually useful.

On some topics they're obviously just going to lie, so you modify your search, or go after the info another way.

I haven't seen another search option that isn't horribly compromised in some way. Some just have shitty results, one of the most popular is run by a customer data seller.