But wasn't this branch of the thread about airlines cancelling flights with low bookings?

Which is it? Are they cancelling the flight with very low booking or are they cancelling the flight which is most advantageous to them? Why are those any different to any significant extent?

What I see, from the inside, is they swap available resources around to protect as much of the operation as possible. It's not always just the passenger count as some passengers are a lot harder to re-route than others. Passengers making a connection to a once-per-day long-haul flight will carry more weight than passengers who have multiple re-route options that same day.

In general, though, the cancelled flight tends to be one with fewer bookings. That is better for the passengers (fewer inconvenienced) and better for the airline (fewer displaced passengers who might cancel for refunds or require other compensation). You have to look beyond just the first cancelled flight, though, as that cancellation may create additional cancellation(s) due to the airplane not completing the first cancelled flight. They're looking at the bigger picture, not just that first flight. That lightly booked airplane may have a return flight that is fully booked with many international connections. We can't see that full picture sitting at the gate (or in the cockpit).