Complex sentence: Besides the construction of floors and interior supports, none of the previous interior designs drawn by Angell and others were executed; thus just as Angell is considered the architect of the temple's exterior, Young should be considered the primary architect for its interior.
Split into simpler sentences: Besides the construction of floors and interior supports, none of the previous interior designs drawn by Angell had been executed. Thus as Angell is considered the architect of the temple's exterior, Young is considered the primary architect for its interior.