>>37106026It's really because of the people who would visit Alolan beaches with their Raichu. Native surfers noticed the Raichu attempting to mimic their trainers when they surfed and how good some of them were at the sport (like anon's pic related
>>37106046 ) and started using them as surfing partners. The Psychic part came from them predicting storms, which was easy for them because of their Electric typing and was very helpful for their trainers to know when the best waves would be rolling in or when it was going to be too strong or dangerous to bother surfing. They eventually began to change over time from being in a different climate until they became what Alolan Raichu are today.
This is
my canon.