So... Difficult to get to Elite Smash.

Your GSP is directly dependent on your win:loss ratio. When you lost, this ratio went from 10:0 to 10:1, thus dropping your GSP by a large amount. This is also the reason that GSP gain and loss is slower after you play several matches.

Although I had already played dozens of matches with Bowser online. Thanks for the explanation though. I feel like it should be determined by winning matches, you gain some. Losing matches you lose some, and how much would be decided by your opponent's GSP.