It was announced yesterday that the former Barcelona coach will take over from Jupp Heynckes at the end of the current season.
Orobitg dismissed the idea that Bayern offered the most money, insisting that Guardiola was tempted by the "potential" of the Bavarian giants.
"It was signed before Christmas, around December 20," Orobitg told EFE Radio.
"Bayern was chosen because of all the teams who made offers it was the best. We went over the offers and this is not the team which offered the most money.
"It was chosen for the organisation there, for the potential and for its players."
Guardiola is currently on a year-long sabbatical after leaving Barcelona at the end of last season.