Conversation so far:
Who is William Hope?
William Hope was a pioneer of so-called spirit photography.
How was William Hope a fraud?
Harry Price wrote in his SPR report William Hope has been found guilty of deliberately substituting his own plates for those of a sitter...“
Why did William Hope do fake evidence?
How did people percieve William Hope?
Despite Price's findings, Hope still retained a noted following amongst spiritualists. Doyle refused to accept any evidence that Hope was a fraud and considered Price's findings a conspiracy against Hope.

Question: Why did he do this?
Self-contained rewrite: Why did William hope do this?