First of all the guy implied that no one is playing him botlane, which is false.
You have to give me some sort of leeway here. I could say that no one plays
as an ADC in bot lane and you could probably find a few players that do. Exceptions to the rule, and all that.
Second, as i said above his winrate got decreased massively (went from like 15% to 1-2%) because he stopped being viable at bot due to the nerfs and the marksman update.
Probably the reason no one's playing him bot lane. Oh sorry, I mean most players aren't playing him bot lane. With the huge nerfs he got after worlds, combined with all the shiny, new toys marksmen got that he can't use, and the solo lane buff he's got coming on the PBE, it's a safe bet to say that bot lane Morde is dead and will soon (hopefully) be a distant memory.
Most people were playing him botlane before.
You mean back when he was so strong he was pick/ban at worlds? Yeah, no kidding. That was almost two months ago, it's not relevant now.
The ones that still playing him in solo lanes are basically the playerbase of the old Morde, which was tiny even before the rework
CerT promised everyone that Morde would be viable both in solo and duo lanes, so it's fair to assume some of the newer players also tried him out there.