Complex sentence: In 1985, after discovering he had contracted AIDS, Rubell (who was closeted for most of his life) began taking AZT, but his illness was furthered by his continued drug usage and drinking, which affected his already compromised immune system.
Split into simpler sentences: In 1985, Rubell (who was closeted for most of his life) discovered he had contracted AIDS. Hegan taking AZT, but his illness was furthered by his continued drug usage and drinking, which affected his already compromised immune system.