Match History? Tell me I'm not paranoid only to stupid to use google properly

Hey guys, So I'm new to HD - and even to steam, I only played some skyrim a couple of years ago. And sth. really creepy happened today. I got stalked and don't know how. A player, who couldn't handle a defeat, didn't only insult me and my mother in all-caps as insert curse words here, no - he also called me a smurf and cheater etc. I don't really mind that person having anger issues and kinda take his insults as appreciation. The creepy thing is, he knew all about my last matches and how many hours I played etc. He even followed me into lobbies and posted my steam-profile there and kept yelling at me in angry capslock. I tried googling it but I didn't find anything like a match history you might know from mobas like LoL. I even tried googling my account and did find only like 10others with similar names. So how did he do it? It would also be good to know if you in general can add people you meet playing as friends via steam. Because some of them really are nice and fun. ;)

For those of you who might be interested what actually happened in the game to make this guy rage this hard and kinda ruin my free day, here's the story:

I used to play casual with friends on gamespy as a teenager back in the days like 13+ years ago and was kinda "good" for a gamespy player (I didn't play zone/voobly so I had no Elo but I knew those guys are way better than us casual gamespy players). I usually played infantry civs like jap/goth/vik/aztec. Today I played a 3v3 green arabia and got vikings (yay!). I was the lowest Elo player in the lobby by about ~70 points. Being new to HD I ofc have low Elo (I don't even know all the new civs yet). But I managed to climb a little already so I'm about 1630 (I also dropped in the 15XX in the beginning). I lost a vill luring boars, got housed once etc. So no great start. But: I was pocket and because I'm really bad at rushing (bf-player⁾ I went 0 military and boomed big after fast castle age. I fast teched champs only (my most practiced build) and raided the enemy pocket player's base with like 30champs while he was busy raiding my flank allies with many knights. MY allies defended well - they resigned. We won (yay again?). Nothing special so far - but then one of the guys started cursing and calling me a **smurf who should die and get cancer, f* myself etc. The usual insults u find with angry internet-kids who prefer blaming some1 else than themselves for losing in a videogame...

So I feel better sharing that experience. And to repeat: I don't mind him insulting me, I played LoL for some years so I'm used to this kind of behaviour, but I'm freaked out how he knew that stuff about my steamaccount ageHD-hours and profile etc. He also said things like "I'm keeping track of you" :(. Thx for reading. Spread some love in the internet not hate <3. ggwp

Edit: I'm also too stupid to write "too stupid" in the title^; non-native speaker here