In terms of market share on cloud computing platforms, Google is currently running third to AWS and Azure, so it makes sense for them to take some short term losses to help build their position.
Whether they will maintain that kind of pricing in the long term, remains to be seen.
They're definitely being aggressive with pricing but they're still making money. Their pricing is definitely way better to deal with than AWS or Azure.
They're just now offering the same tech to the public with GCP products like Compute Engine, Spanner, BigQuery, etc. which shows in the level of sophistication and performance compared to Azure and AWS.
You obviously feel that Google's services are more advanced than Microsoft's and Amazon's but from a market share perspective they're clearly running third to those two.
All 3 majors have great tech but Google has been doing much more advanced stuff which can be seen directly in their products. Everything in GCP is seamless from scaling without warm-ups, per-minute billing, automatic discounts, custom vm shapes, live migration, truly global load balancing, etc... and that's just in their compute engine product.
They're providing you something for free, which costs them money to provide...
At Google's scale, unless you mine bitcoins and actually use CPU/GPU time, the money Google actually spends on your tiny $300 free trial is maybe worth a dollar or two (and if they run free trials on machines that are paid off in terms of taxes, the only "expenses" are a tiny tiny sliver of maintenance - at Google scale network connectivity is basically free).
Cloud providers, especially for 24/7 running services, are a total rip-off even compared to managed servers, and deploying your own bare metal will blow any cloud calculation away when you're getting serious (> 200GB RAM, 50+ cores). The real strength of cloud is when you need extremely high computing power for very short time (e.g. heavy software builds, occasional transcoding, ML training).
And it's opportunity cost we're looking at here. It may only cost them a small amount to provide the resources (although that ignores the cost of developing/maintaining the services) but if they provide $300 of credit to one party that's resources they're not selling for $300 to someone else.