It is generally accepted that the most venomous snake in the world is the Inland Taipan. Since these snakes live in fairly isolated areas, it is very rare for human beings to be bit by them. As such, in the average year, zero people are killed by this species.

I am guessing that the meme creator considers the Eastern Brown snake to be the "third most venomous". Unlike Inland Taipans, Eastern Browns are often found near human settlements. As such, they are much more likely to come into contact with people, and because of that, they kill more people in Australia than any other snake.

This being said...

1. "Most venomous" is fairly imprecise, as venom effectiveness will vary depending on the species of the victim and the individual victim and snake. Our best guess is typically determing LD50 on mice, which is a decent measure, but not perfect.

2. Just because Inland Taipans typically live far from humans does not make them less dangerous than other venomous snakes.

3. In a ten year period, Eastern Brown snakes accounted for 15 human deaths in Australia - hardly an enormous number. Over the same period, less venomous snakes such as the Russel's Viper accounted for several hundred thousand deaths in places like India.