I'd be curious to hear if Microsoft buying GitHub had anything to do with it as well.
They adopted Kubernetes relatively early, and as they progressed their reliance on Azure-specific services went down. At that point move to another cloud was a purely financial decision.
The move to k8s was not strictly a means to allow cloud migration. GitLab sells their Enteprise product, and the Kubernetes-based deployment helps customers with product trial and adoption. Cloud migration is a welcomed side-effect of that initiative.
And this is the promise of k8s for companies (and the peril of k8s for cloud providers).
For just one tip of that iceberg, this Wikipedia article seems like a good place to start:
> In order of descending priority. Most important goals at the top.
1) Use the opportunity of an inter-cloud migration to make GitLab.com suitable for mission critical client workloads Migrate GitLab.com from the Microsoft Azure Cloud platform to the Google Cloud while keeping downtime to a minimum
2) Use the same helm charts for GitLab.com as our EEP customers use
3) The goal here is for customers to be able to spin up a 10 person GitLab EEP instance in Kubernetes and scale it up to 100k users (or more) with little effort.
4) Use the migration as a marketing opportunity for GitLab Inc through creation of technical content
You are unlikely to find an explanation in their docs.
Here's a likely answer:
> Kubernetes? Yeah right... The reasons are very clear: 1) GitHub being acquired by Microsoft. 2) Google is an investor in GitLab (through GV).