Official election results give Tikhanovskaya 500k votes, Telegram poll - 1M votes, 2x more.
Its possible that some of the people in the Telegram poll are not eligible to vote (due to age or whatever).
There could be other issues like people changing who they voted for in the election after previously voting in Telegram.
People behind this campaign are starting to reveal their names at last. I know personally one of them.
My network says others are highly respectable as well.
From what I've seen of reporting in Belarus, nobody watched over the shoulder as people filled in their ballots. It's still a secret who any specific individual voted for (unless they choose to tell you).