> It's not clear how much of this was caused by Legoland and how much Legoland is just an example of bond market troubles

It is pretty clear. Almost every single report on the bond market attributes this incident as a direct cause of the turmoil. Sentiments drive the market and this is a signal strong enough to spread FUD among the market. If you cannot trust government-issued bonds, then what else you can trust?

Of course, this is not the sole reason. Your question is more of a counterfactual reasoning, like "would it happen if the market is in a better situation". It might be better, but you are not supposed to throw embers when oil's leaking.