Once infections beacme easy to treat there was less emphasis on avoiding them (and we are talking about wahsing hands here, not something complicated).
It's not quite as easy as just blaming NHS staff (and contracted cleaners). It's also got a lot to do with the fact that now one can go to visit in-patients nearly all day long. "In the olden" (not always golden) days there were very restricted visiting times (1 or 2 hours per day), which made cleaning after 'the general public' was around much easier and therefore also kept all the various illnesses they brought along at bay.
And I'll never for the life of me understand why here in the UK they STILL build hospitals with rooms/wards for more than 4 people. It really beggars believe!
I was absolutely horrified when I moved here 11 years ago to find open wards for 15 people and more! I had never seen anything like it.
It just doesn't matter how clean the wards may be - things like C dif just spread like wildfire to all patients in such wards. Patients don't wash their hands every 5 minutes, nor do they tend to use a mask when sneezing or coughing.