Were the mansions burned down to expose the passageways?

[Optimism is my Phil-osophy]

Olaf claims he wants to destroy all VFD properties in TGG. Despite this, the exposure of VFD to the public was not Olaf's personal goal, but one of those in TDP.

[Hermes]

Olaf describes himself ans an independent practitioner. It doesn't look as if the villainous side of VFD generally operates as an organised body. I take it that the sinister duo protect them, and so can call upon their loyalty where necessary - and near the end of the series they are hatching a plot - but most of the time it seems to be a matter of individual villains committing individual crimes for personal gain. Also, while the sinister duo clearly are plotting against VFD, they also seem to enjoy burning things for burning's sake, as in the passage where they threaten to burn down all the snow scouts' parents' homes, though the scouts don't all seem to come from VFD families.

It's true we don't actually know who started the Baudelaire and Quagmire fires, and it could have been the sinsiter duo, in which case they very likely were targeting VFD; but I think it in that case would just be a matter of eliminating some of its leading members - in any case the passages aren't exposed, so there would not be much point in trying to do that.