I've only thought about it for a minute- but I might speculate that it is a signal from Russia- "even if we decide we want to turn the gas back on, you might not be able to get it when you want it."
Also, Biden promised that they had the capability and desire to take out the pipelines if Russia invaded so there is that. Plus, the US would stand to profit from exporting LNG to Germany.
Dear Russia
Thanks for confirming so clearly that you are an untrustworthy and manipulative partner.
Best,
-The Rest of Europe.