That was just the current management undoing their predecessor's idiocy of losing their original place in the mobile market.
It's easy to forget how disastrous things looked back then; BT had monstrous debt following the mobile auctions and its peak valuation was just prior to the dotcom crash. Creating and divesting mmO2 was to essential to keep things afloat.
You could argue it worked - shares were worth a shade under 83p when mmO2 was spun off and Telefonica later bought it for £2. By comparison, Vodafone's price was (about) 220p when mmO2 was spun off and (about) 175p in Oct 2005 when Telefonica's buy-out was agreed.