The reason why support miss fortune was picked by ROX Gorilla
- it was a counter pick. -mf Q counters zyra plants (free double-up nukes in lane if zyra ever tries to be even slightly aggressive) -no one in SKT had immediate hard cc to interrupt mf ult (i guess u can argue orianna does have immediate hard cc but she still takes a second or two to set up the ult)
- synergy with ashe adc. -mf's E was used to setup ashe's ult -ashe's ult in turn was used to setup mf ult -notice how ROX first picked ashe instead of other champs in game 4
- And early game pressure -but no one in your elo probably takes advantage of early game pressure unless you are in somewhere around diamond+ with voicechat
TL;DR: for the love of god dont play mf support unless u actually know what you are doing
Edit: im no challenger player, but these were said by LCS analysts and all im doing is summarizing their analysis