Simple answer: There are actually two good and well-known (at least, I had thought so) bibliographic databases for mathematical literature:
The latter is freely available online as of 2021.
(Of course there are a few differences between them - for instance, the quality of the bibtex entries is a bit better in MathSciNet, in my experience. But anyway, for most purposes both databases do their job quite well.)
Historical Note: While MathSciNet is essentially based on Mathematical Reviews, zbMATH is based on the Zentralblatt für Mathematik - and both the Zentralblatt and Mathematical Reviews were founded by the same person, Otto Neugebauer. I would have called this a fun fact, but unfortunately the historically background (which is described in the previous link) is not particularly funny.