Where do I start?
Firstly, this individual is not known to have committed hundreds of rapes. There is a suggestion, from police, that he could have commmited more than a hundred sex assaults (not always the same thing as rape) but that is speculation.
Worboys was convicted of one rape, a handful of sex assaults and a few offences of administering a stupefying substance (likely under OAPA). This is all he could therefore be sentenced for.
The CPS generally do a reasonably good job in difficult circumstances. Sadly, when someone alleges a sex assault or rape months or even years down the line, it is almost impossible to prove this to a legal standard in these types of instance (no longer prospect of DNA, little recollection if drugged etc). Therefore, there can be absolutely no prospect of a reasonable and fair jury convicting on those accounts.
Awful that's the reality.