Look at it this way, Orthodox Jews do not date or marry non-Jews. Yet he very much indesputably dated a non-Jew for years. Put aside the public photos and news reports of him eating with her in non-kosher restaurants long before her father ran for president (those photo stories are still online from the early 2010s). And let’s not kid ourselves that he brought his own kosher food to the super fancy non-kosher joints he was taking her to. Why would he go to that restaurant on his date with her if he was bringing his own food? Do you really kid yourself into thinking that while he was dating a non-Jew he was keeping kosher and living an Orthodox/halachic life?
So clearly he was not observant long before marriage. Does anyone actually believe that when she underwent the process she intended to become observant when her fiance was not?