RFU presumably very confident the deal will be done in a week or more likely very confident it won't be so giving an extra week makes no difference but looks like they are working with club.
Pretty sure he thinks he might be able to pull it off, and calculated that 50% would just be enough.
Pretty sure the RFU was terrified of yet more backlash if they simply pulled the plug today. They made it 7 days from yesterday's deadline, because that was what they offered in the first place.
I would bet they are now very worried if the deal is made, and then it is left to the RFU to approve the deal and new owners. My guess is that Crossan knows that the RFU would not approve, and so he and the buyers have backed the RFU in to a corner of submission. We will know that is true if said buyers go through with the deal at the last minute next week, forcing the RFU to give another extension to allow them time to check the new buyers out, all the while under pressure from everybody.
To be fair, it was their own incompetence in allowing Irish the first extension back in April. From that point on, Crossan has been gaming them, in a giant game of poker, and the RFU have played their hand very badly. Today is just another example of how poor they are at business.