being flamed after games usually happens to kirbys or fox's who spam lasers.
With good reason, your laser spamming is possibly the most annoying thing ever.
I've only been playing about a month too, but I've noticed that the past 2 weeks have been especially bad. Sometimes it's not just people flaming you but just being annoying on purpose. One example is when someone pauses the game repeatedly to annoy you.
Earlier today I was playing a Kirby, I managed to get him down to his last life without getting killed, but I was at about 100% damage and he managed to get me with a smash attack which kills me, and then he immediately pauses and drops out of the game, pretty lame but I laughed at how immature he was.
In general Smash is a pretty emotional game in the first place. Losing does suck, and a lot of people will get angry. Just keep calm and whatever. It's just a game, you can't avoid it, and the Internet is full of idiots anyway.