Perhaps someone legal could answer but could it be that the judge has to allow it as admissable? The defence may have objected but it is relevant. It shows a man that has been offending for a while for starters. One who likes to terrorise women. One who wouldn't try to kindly take a crying girl home.
it is a very long time since I studied this - so this is only a general overview
Evidence of bad character IIRC is typically not allowed unless the defence opens the door to it via its own evidence (e.g good character)
The Rule against Similar Fact evidence. Typically similar fact evidence is not allowed due to the dangers of propensity reasoning. In other words, the accused probably did this because he is the type of person who would rape and murder a girl. This is a logical fallacy.
However, where similar fact or prior offending is specifically relevant, it may be admitted.
IMO in this case, the judge likely allowed the evidence for the following reasons
1. His lurking and stalking is material to his reasons for being in the area that night. For instance if he was in the area for innocent reasons (he says running) that is critical to motive. But the other crimes show he was routinely lurking, stalking, and offending in the area - that goes to motive and should be allowed so the prosecution may demonstrate that he was in the streets that night looking for opportunities for sex crimes.
2. Seemingly masturbating in the street after the murder - again typical of his established MO. Relevant to disproving the accused's police statement.
3. Sexual assault - his long track record indicates an MO of lurking in the area to commit sex crimes, where women felt in danger.
I am sure the defence argued that the prior offending was all of a voyeuristic, exhibitionist type, with no sexual assaults, but I believe it is also the case that the breaking and entering type of offender, often graduates to rape.
