Reading between the lines here I'm getting the sense that you think being fired is a huge red flag that should be a career stopper. To me, this, and scrutinising gaps in someone's resume feels archaic and a little bit sad. People leave companies for many reasons, reasons that in the past weren't quite understood. Mental health issues, addiction, changing priorities, motivation burnout, culture fit.
Leaving a big company like Google doesn't mean you automatically got fired - not everyone considers tech giants to be the end game. I worked for a short while at Apple and hated the silos. I had no insight into how my work was helping the mission and I couldn't give feedback to my managers or team. Even worse, I wasn't convinced my work was being used for anything, so I left. Am I unhirable now? I'm still going to use ex-Apple to get work that fits me better.