The reaction to disconnects and crashes is different depending on how far into the game it is. Before a certain point, the whole game just gets cancelled, and everyone kicked out. That sounds like what portion of the game you were in. I haven’t ever seen someone able to rejoin during an early game DC. I’m not sure you can even rejoin.
If you’re convinced there’s nothing wrong with your computer, then you’ll want to go to the Tech Support forums and follow their instructions for how to post a crash problem and get assistance.
I’m not blaming you, or even your computer. I just gave advice on what the basic things to check would be. The tech support forums have more thorough steps that you should go through.
Most people do not have crashing problems.
The penalties are to discourage intentional leaving. It’s nearly impossible for the system to differentiate between an innocent crash or disconnect and an intentional one to leave a game. That’s why the penalties exist.
Also, the SR loss is temporary. You’ll gain more SR on your next several wins to catch you back up to where you were.
Recovery from disconnecting is identical to recovery from decay. That is, after a single disconnect a player will have an SR buff for about 12 games until his SR has caught back up to what it would have been if he’d never disconnected. Because leaver recovery is identical to decay recovery, it is likely that MMR is unaffected by leaving, just as it is unaffected by decay.
Quote from “Leaver Penalty” section: