My current theory on this, particularly for Google, is they're just taking advantage of the macroeconomic moment to cut some fat. Slowing growth or outright letting people go is a no-go in times of macroeconomic growth. Big companies, even if not strictly needed, can be opportunistic here and make some cuts they wouldn't be able to in other circumstances.
I agree and find the attempt at a breakup a bit frustrating. This is an action that could have profoundly disruptive effect and it's not really clear what the positives or negatives would be. For instance, FB has invested massively in trust and safety people operations and AI. What happens to that investment when IG is spun off?
Laying out laws and regulations so the market works as intended (no doubt with adjustments on the way) seems like the far preferable way to ensure healthy competition than taking a hammer to the job site and hoping for the best.
I suspect part of the motivation is to scoop the reporter's own story as a passive aggressive reprisal. It also serves to reduce the chance of future reporters on negative topics to talk directly to Coinbase since they've already showed they're willing to break stories before they publish.