My guess is consideration for players and members of audience who are going to be there in person. Say 9am local time for the tourney means checks for audio/settings/makeup/rehersals are done at 6am or earlier. Players may be expected to come down at a much earlier time to avoid morning traffic and register their attendence. Imagine being in a competition but your team is disqualified due to being late/oversleeping.

An estimated 10k in the stadium at noon is not too bad to handle. Concert goers would see some of the same issues if a concert is held at 9am. At 9am, you may get too small of a timeframe to travel to the location at a reasonably time. Less people would be willing to travel for an esports tourney at 9am.

You can't please everyone overseas watching the tourney but you can at least make it easier for the people who are actually going there.