Cause of him destroying the control ship. Plus viewing him through the mind stone just as he had for Loki.

Everyone in the universe knows Tony Stark for some reason.

Cause he's kinda the first human with mass alien murder on his hands.

I guess Thanos has his way of knowing

Who knows maybe when Tony destroyed the Chitauri army Thanos was informed by The Other which is where revealed who destroyed it

Thanos had his means of investigating, so he learned all about Stark after the Avengers won the Battle of New York.

^you mean Thanos not Thanks

Maybe the Reality Stone gave him awareness of people's real names?