How was this a draw?

I don't get it... There are 5 kinds of draw.

1) Stalemate, both sides have plenty of moves. Not this one.
2) 50 move rule. Not this one for sure, I moved a pawn 6 moves prior to the draw.
3) Draw by agreement. Not this one for sure either I never hit the draw button.
4) Draw by insufficient material. Not this one for sure both have a rook so not possible, had I been flagged it's a loss.
5) That leave draw by 3 fold repetition... I'm pretty sure it was only repeated twice so...

How was it a draw, or was it a bug?

Looks like the position was repeated only twice, but I highly doubt it's a bug. Hopefully one of the experts will chime in...

3 fold repetition, moves 86, 88, and 90 were the same position

I don’t get why so many don’t know elementary rules. Probably the US does a good job hiding the rules.

I wouldn't say in the US we hide rules any more than any other country in regular events.

Scholastic events in the US though? Phew you better be prepared for some truly awesome displays.

So draw by repetition is a repetition of positions and not moves? I didn't know that. Also, only 1 side needs to have repeated 3 times, and it doesn't need to be sequentially?

I dunno this position just don't feel like a typical "draw by repetition" Very much a technicality.

1) The 3 repetitions were not all in a row
2) The 3 repetitions only happened for one side
3) The 3 repetitions did not use the same move all 3 times to reach the repeated position

Three fold repetition only looks at board position (and if the board contains all of the same legal moves - think castling and en passant). The only question you need to ask is 'has this exact board position been seen three times this game with the same player to move?', if yes, then it is three fold. Doesn't matter how the board got into that position at all. It doesn't even matter if pieces have swapped places, such as two rooks or two knights. Technicality or not, those are the rules of chess.

I think players have a hard time since they can't remember previous board positions very well and so they are used to three fold only in cases when it happens on consecutive turns - it's easy to see if two players are just moving two pieces back and forth.

My personal rule of thumb: if the FEN‘s are the same

Right, your 3 points in #6 are all irrelevant - that's a common misunderstanding.
@willsch has explained it well, next time you just play 90. f6# and save yourself the trouble. ;)

@willsch thanks for the explanation.