A lot of the layoffs are international, so if they had announced on Friday the employees would have learned of their terminations over theirs weekends, as Friday in the U.S. is generally at least Saturday in Europe and Asia.

International companies generally announce cross-border layoffs on Monday (US-time), because that announcement will be during the work week everywhere they operate.

The most reasonable explanation is that they were targeting Friday, but were late and so it was Monday. Firing 3,000 employees takes a lot of preparation. If there are a few corner case employee resolutions, that holds up the whole bunch

And there are legal steps they will have to go through making redundant that many in the US

Friday in San Francisco is Saturday in Asia which means there's probably a layoff on Monday in Asia.

However a Monday layoff in San Francisco means a Tuesday layoff in Asia which won't be separated by a weekend.

What is the line of reasoning that favors a Friday for layoffs?

Not OP, but a lot of American companies do layoffs on a Friday in an attempt to have fewer headlines on a weekend (news outlets aren’t fully staffed then, people are distracted, etc.)

https://www.kornferry.com/insights/articles/bad-news-deliver...

There are several, one is that you can time it with payroll, so your last day is the end of the current payroll period, just makes it neat for accounting purposes.

Another is that if the company doesn't want the media to pick up the "bad news", Friday is the best time to do it because it'll get lost over the weekend when it's reported on.

And finally, there's less worry about retaliation from disgruntled employees if they have the weekend to calm down over being let go.

I think he/she is saying that announcing bad news on a Friday usually helps because it mitigates the amount of negative coverage it would receive from the media. Announcing on a Monday then seems unusual from a PR perspective.