And there weren't many things that Bishop Alfred Mendez did that were, say, somewhat "scandalous"? Bishop Thuc certainly seemed to be easily manipulated by strong personalities, but that has nothing to do with the validity of the consecrations; all he would have need to validly confect the Sacraments was a basic understanding that he was doing what the Church does to pass on the episcopacy. Prudence and judgment and personal virtue have nothing to do with it. Bishop Mendez, on the other hand, had suffered a stroke not too long before the consecration of Bishop Kelly and reportedly did not recognize one of his close relatives. To me there are greater questions about the Mendez consecration / ordinations than about the ones performed by Bishop Thuc.
According to witnesses, every time Bishop Mendez got to the essential words for the ordination of Fathers Greenwell and Baumberger, he mysteriously sped up and garbled the words. Father Kelly had to ask him to repeat them several times. He had said everything quite clearly until the actual words of ordination. Father Kelly later said that he would never do that again. Bishop Mendez for the longest time publicly denied having ordained these men, and the consecration was never made public until after Bishop Mendez' death. Bishop Thuc, when later asked about the consecrations he had done, never denied them ... even if sometimes he regreted a few. I know a priest who sat at table with Bishop Thuc. There were priests who spoke different languages there, and Bishop Thuc could switch from one language to another without skipping a beat. He clearly was in sufficient possession of his mental faculties to validly confer episcopal consecration.