IMHO a better move for them would have been to clear up the legal minefield that comes with AGPL and move to a more business friendly license like the Apache 2.0 or MIT license. These licenses are well understood and don't cripple your users in any way.
I don't get why any business would want to scare their new users with a license like the AGPL that I would argue is explicitly designed to create legal uncertainty like that and popular with companies like Mongo primarily for that reason (as opposed to some strong freedom related moral arguments). Inventing your own license because the AGPL is giving your users to much freedom sounds rather desperate (not to mention misguided).
Changing the license to Apache 2.0 might actually make them much more attractive as an acquisition target for any of the big tech companies out there looking to add something like mongo to their portfolio. I'd argue AGPL is actually an obstacle for most of the bigger companies out there that have existing business relations with their customers based on more business friendly licenses.
It would also enable lots of people to experiment with using mongo without legal worries and thus enable them to refocus their company around actually creating value for their paying customers without alienating the vast majority of non paying users with complicated licensing options.
Companies like Elastic (which recently did their IPO) are having plenty of success with using the Apache 2.0 license without compromising on commercial success. Their developer ecosystem includes lots of outsiders in the apache community, the academic community, and users. The reason they are doing pretty OK is that they have a decent monetization strategy that involves delivering actual value to their customers: stuff their users want and are willing to pay for. Stuff like proprietary add-ons (e.g. machine learning) on top of what they ship for free, good support, training, cloud based hosting, consulting, etc. We use their hosted Elastic cloud and I'd argue it is pretty good value.