But why now? There is no wavering at the moment. They could have waited a month or two, to see if it's actually needed, because the downside of discovery is so high. And why does the CIA warn about attacks then? False flag?
Another option is that somebody wanted to plant explosive devices for future use, and something went wrong. Hard to see how both pipelines would blow up then, but maybe a possibility.
If Germany and Russia were about to kick off negotiations to bring nordstream back online then it would all but confirm that an ally did it (probably America). This would be far more likely to happen next month as Germany really starts to suffer.
Whoever did it picked pretty much the perfect time from the perspective of deniability.
As said before, it would be to prevent Germany from caving and turning the taps back on in winter when they are desperate for gas.