GiveWell began to focus more on marketing in late 2017. This particular post doesn't mention SEO, but others might (Googling "GiveWell marketing" brings up quite a few results for me).

The most important point from that post: Almost all of GiveWell's funding comes from large donors ($2000 and up), who are probably less likely to start with a search engine compared to other sources. The audience they can reach through Ezra Klein's podcast is probably much more promising than the Google search audience.

I'd also suspect that Google ads are more competitive than podcast ads; Charity Watch might outbid GiveWell if they go after the #1 result for "best charities".

As for 80,000 Hours, I'd guess that they are like GiveWell but even more so; almost all the people who might find their site from a search like the one you describe are likely not to be a very good fit for their coaching, and perhaps not even for their advice (since many of the jobs they recommend are easiest to obtain for people with degrees from highly-ranked colleges -- people who are perhaps less likely than the average person to use Google for this sort of thing).

But this is just a guess, since I'm not sure whether 80K has published data on their marketing strategy or where they hear about the people they end up coaching.

ea in general has no mainstream exposure except that vox series