Why did Morrisons close and sell all of the Safeway UK branches instead of a partnership such as Wal-Mart and ASDA?

Morrisons converted the majority of Safeway stores into Morrisons, the remainder were sold due to local competition issues to Tesco, Sainsburys, Waitrose etc.

The Safeway brand is no longer in use in the UK, as Morrisons decided it would be better to rebrand all stores as Morrisons.