No, China didn’t have anything to do with Corbyn. Just, right before he took control of the party, the party leaders tried to vote him out. There are over 10 million labor voters, but at the time there were only 100,000 paid labor memberships, who were responsible for voting in the party leader. Corbyn got 50,000 (out of the 10 million) new paying members on the rolls and went over night from being on the edge of being expelled to becoming the party leader.
Same thing happened here: a very large group (all scifi readers) assuming that paying members would have ideals proportional to the larger group - but that smaller group can be manipulated through a large influx of single issue voters.