Complex sentence: After his death, Mary married Archduke Maximilian I of the House of Habsburg, who later became Holy Roman Emperor; thereafter the Burgundian Netherlands came under the rule of the House of Habsburg, thereby beginning the period of the Habsburg Netherlands (1482--1581).
Split into simpler sentences: After his death, Mary married Archduke Maximilian I of the House of Habsburg, who later became Holy Roman Emperor. The Burgundian Netherlands then came under the rule of the House of Habsburg, beginning the period of the Habsburg Netherlands (1482--1581).