Insincere conversion to Judaism?

Hi,

"One who converts in order to partake of a royal table, or to be among Solomon's servants, is not a valid convert, per Rabbi Nechemiah. For Rabbi Nechemiah said: Those who have converted for fear of wild animals or due to dreams, and those who converted in the days of Mordechai and Esther, are not valid converts…

"Rav said: The law follows the view that they are all valid converts [after the fact]."

(Talmud, Yevamot 24b)

Have a great day,
Mordechai