Answer :

I believe the answer is: it needed protection from Germany

At that time, the France empire faced the largest threat in their history, since the Russian Empire set their eyes on them and wanted to take them out. Because of this, France joined the Triple entente to obtain protection from Germany which might be the only empire at that time that can take on the Russian Empire.

France joined the Triple Entente because it needed protection from Germany.

The Triple Entente constituted the alliance which joined the Russian Empire, the French Third Republic, along with the United Kingdom of Great Britain and Ireland following the signing of the Anglo-Russian Entente on 31 August 1907.

The French Third Republic was the system of government adopted in France from 1870.