I find it difficult to believe he was infatuated with Joanna, when he had only known her for a few days------unless, of course, he had met her before. That's what we don't know!
He appears to have been very close to his partner, Tanja.
Isn't that also speculation?
However .....
His computer history showed that
"on the morning of 7 January - weeks after JY's body had been found - Tabak searched for "Jo Yeates" on Google, minutes before moving on to the violent pornographic sites
"Some of those films contained images of a woman again being held by the throat," Mr Lickley told Bristol Crown Court.
And some recovered images showed a petite blonde woman with her top pulled up in a similar fashion to how Miss Yeates was found.
"That suggests he derived sexual pleasure from them," said Mr Lickley.
"He received a text message from his girlfriend but continued watching the pornography."
https://www.bbc.co.uk/news/uk-england-bristol-14904647