According to The Telegraph, a French MP demanded an inquiry be made into Steve Bannon's links with Marine Le Pen:
Mr Lefebvre made the demand in an open letter to the heads of the National Assembly’s law and foreign affairs committees after the public television channel France 2 revealed alleged close links between Ms Le Pen’s party and Mr Bannon.
Wikipedia confirms Bannon's support for European right wing populist movements:
Bannon is supportive of several European right-wing populist national conservative movements such as the Hungarian Fidesz, the French National Front, the Spanish Vox, the Dutch Party for Freedom, Alternative for Germany, the Italian Northern League, the Brothers of Italy, the Freedom Party of Austria, the Sweden Democrats, the Finns Party, the Flemish Vlaams Belang, the Belgian People's Party, the Polish National Movement, and the Swiss People's Party
I can understand that association with a US political figure might influence French voters, but why the need for an investigation?
Question: Why are Marine Le Pen's possible connections with Steve Bannon something worth investigating?