If shut down is in the plan, the move to the Google cloud doesn't completely makes sense, unless they think the big names customers will attract more adopters?
They would acquire users and data from one of Keep's largest and most established competitors short of MS OneNote while simultaneously removing them as a competitor in the market. Seems like a pretty solid incentive if Google is serious about staying in that space.
Step 2: Migrate to Google platform.
Step 3: Exit via Google acquisition.