Virgin set up True Blue to be as big as it was commercially. The craze and phenomenon during the Virgin era >>>
The imagery and songs of the Virgin era are more associated with Madonna. True Blue was just a byproduct of how big she was at the time and continuing momentum on a gl0bal scale.
Sorry, but releasing in time periods with less competition doesn't make your album bigger. That'd be like saying Sia's last album was bigger than In the Lonely Hour because the former debuted at #1 despite only selling 52K and the latter peaked at #2 with triple the amount of sales.
Actually, you're wrong. There's more competition. In 2014 the most albums were released in history according to Soundscan/RIAA. The number goes up every year. Especially with the way anyone can independently drop an album in 2015, versus in 1975 nobody could put out an album unless a label signed them.
And lols, you're comparing 1 week. Billboard doesn't compare 1 week. They compare overall runs.