Yes, Bobby Fischer made a massive blunder, but keep in mind. This was the only game in that match where Bobby lost like this. In fact, this match in one one of the most impressive performances in the history of Chess. Bobby destroyed Spassky and won the World Championship.
In this game, we see the World Champion Garry Kasparov make a mistake costing him a game in the World Championship match against Anatoly Karpov.
Rook to a1 was the famous blunder that brought the game from about even to +13 on Stockfish, the strongest of Chess engines. Kasparov was low on time which is likely the culprit for making this famous blunder.
Magnus Carlsen vs Viswanathan Anand – Sochi RUS, rd 6, Nov 15, 2014
After the Kan variation of the Sicilian Defense was played, White finds himself in the endgame with a horrible pawn structure and Black is left vulnerable due to most of the pawns on light squares against a Dark Squared Bishop. Also Anand is in an endgame that’s about even with the best endgame Chess player of all time which is a disadvantage by default.
Even being the best, Magnus Carlsen is the one in this game that made a blunder that immediately loses the game. Magnus plays King to d2 on move 26.
However, in this game, it’s the first time where a double blunder was made. Anand misses the opportunity to win with the following move. Anand plays a4, missing the win and giving the advantage back to the World Champion.