There are several reasons for that change in eSports.
-The huge flood of money into eSports scenes, from various sources such partnerships with sports teams or large corporations, Venture Capital funding, or rich people that want to own an eSport team as their personal toy. This leads to players and teams needing to be professional, as well as ensuring good performance in-game, to keep the sponsors satisfied.
-The rise of Korean players and teams, who practice for long hours daily, and have very little personality player and team-wise, who then start dominating in tournaments, which then makes other teams have to adapt to similar practices to keep up with them. Do note that in the games where Koreans aren't dominating in them, i.e. DOTA 2 or CSGO, the practice routines for teams aren't as extreme.
-Gaming companies are trying to push their games into being the Next Big Thing in eSports, due to all of the money flooding in.
Going back to MTG though, according to Wizards' TOS about fan-content for the game, drawing Rule 34 of MTG characters is not allowed, although I'm not sure if WOTC ever went after someone for drawing MTG porn. It is telling though that amount of R34 for MTG is a lot less, compared to most other fandoms.