You can see my extended explanation above, but in short it was due to a glacial moraine outburst flood upstream, releasing two-thirds of the water of Lhonak Lake in one go. The lake was known to be at high risk of bursting the moraine.
The lake itself was caused by glacial melt due to global warming, first appearing in the 1960s. The bursting of the lake this summer will almost certainly be traced to the record high temperatures recorded this summer, which led to an increase in size of the lake and overtopping the moraine that held it in place.
This article has satellite images showing the recent growth of the lake and then the recent release of most of its waters:
Assuming the Santos seat flips Democrat, the house goes from 222-213 to 221-214.
So a 9 vote margin to a 7 vote margin.
It is mighty thin indeed…
For comparison, in the previous Congress the Democratic majority mostly ranged from 218 to 222 (for the last couple of weeks of 2022 it was as low as 216-213 due to resignations etc). See
https://en.m.wikipedia.org/wiki/117th_United_States_Congress