I think people forget how much of the Laurel REY already have....

I think people forget how much of the Laurel REY already have. There is a high probability they end up with more than OBL even if they don't get 50% of Derby (there aren't really many scenarios I see where OBL end up with much more than 25% after a farm in).
That said OBL has more leverage to their Laurel than REY does to theirs now OBL's SP has tanked.
If REY get hold of 50% of Derby OBL will be the smallest Laurel player out of the three (but still highly leveraged, which to a point is what matters).

I think it's just opportunism. If you could increase your ground by a substantial margin for a lousy couple of hundred thousand then why not? I mean for a 2% royalty they can get what Buru was going to pay $3M for if it works out for them. Bit of a no brainer given the ROI. Will be a coup if it works.