He has 82 million followers. That’s a lot of people to be completely biased. Granted, it’s not half a billion for completely unbiased sample, but still, that’s a lot.
a) Either followers of Elon
b) People the Twitter Algorithm decided were most likely to interact with it -- I.E. people who would be interested in what Elon has to say
Just because Elon tweeted something doesn't mean all of Twitter saw it.
If you polled the audience at a regular-season San Francisco Giants home game against the Los Angeles Dodgers as to what team they support, you'd probably get an overwhelming number of responses indicating support for the Giants. That does not mean more people support the Giants than the Dodgers in Los Angeles. They're two different populations, so you can't generalize the outcome from one to the other.