You really think the firm is taking an upfront fee or retainer for this? I assume they are expecting a settlement from Google/Alphabet so that the company can put an end to this PR nightmare once and for all, from which they will take a cut.
A PR nightmare for him costs him very little. There are no products that customers can boycott to get back at him. No offices where he could be protested.
The 'worst' that could happen is that some tech companies refusing to hire him. But given his recent fame, I doubt he has to worry about money anymore.