Dewani surfed porn and gay dating sites for the same reason as many other people do. For comfort. For solace. For distraction. Or for any one of a myriad reasons. Whether some people wish to accept it or not people do deal with grief in vastly different ways ranging from near suicidal plunges into despair right through to an outer appearance of blank indifference and forcing oneself to "keep calm and carry on".
Dewani, by all accounts, showed a range of emotions and actions. Peolple like Passer-by and puglove focus on his internet searches yet that ignores the glaring evidence to suggest he was genuinely distraught at his wife's death.
Any law enforcement person will tell you that the one sure way to head down the wrong path in an investigation is to be led solely by the emotions of people involved. The person who cries loudest may be the perpetrator. The person who appears unmoved at the funeral may be the one who commits suicide ten days later, unable to cope with the grief.
If there was no other evidence in this case then I could understand people paying attention to Dewani's internet usage but considering the overwhelming evidence to show the "murder for hire" story was made up, focusing on this angle makes no sense at all.