Two other important details:
Big tech just spent the last 2 years hiring like crazy. Amazon doubled it's workforce from ~800,000 to 1.6 million, while they had already exhausted most of the labour pool. Google itself grew by ~30%. As a result, pay ballooned as these companies fought over the same tech workers. This is slowly cooling off again.
Big tech has started to get a reputation as shitty workplaces. As such, they have to pay premiums on their salary. On top of the working conditions, products like Facebook or Stadia aren't "cool" projects to work on. You could get $150k at [generic large company], so why bother putting up with Zuckerberg's bullshit or Google's internal rat race, unless they pay more?