I see this as a good thing overall. One big well backed operator (BT/EE) with 3 smaller operators isn’t really working. The smaller players simply don’t have enough to fund a decent 5G rollout. If the CMA really wanted 4 players they should have blocked BT grabbing EE and Ofcom would have needed to have done a better job allocating spectrum.
I do now worry for O2 however. They are going to be much smaller than the other two and have very little 5G spectrum. They also have a mast sharing agreement with Vodafone, will be interesting to see if that lasts.