Oh absolutely. I don't think they really thought they could force Amazon to license MongoDB, but I do think they believed they could force Amazon to not offer something that competed directly with Atlas.
That hasn't worked out for them very well.
(Not that I think leaving the license alone would have worked out any better. To the best of my knowledge, the MySQL, Postgres, Redis, and Memcache projects have not particularly benefited from Amazon building RDS and Elasticache on top of them, and I see no reason to think Amazon would have contributed a bunch of great patches upstream for MongoDB either.)
Unlike MongoDB, it is a real volunteer-led open-source projects, and the goal is to provide an excellent database to users rather than make money. Having easy-to-use cloud hosted versions available helps with attracting users, mindshare, and perhaps in the long run developers to the project itself. Having cloud hosted versions from big vendors means that it's easy to justify "we'll use PostgreSQL for this project" to management or clients.
Was that even the goal? My impression of the licensing change was not that they expected to Amazon to pay fees for offering a hosted MongoDB service. It was instead to lock Amazon out, and keep MongoDB Inc. as the only "cloud provider" of a hosted MongoDB service (perhaps still on top of AWS but with separate management interface).