Short answers, pulled from the story.
Tappi Iwase composed the main theme for Metal Gear Solid. He crafted an auditory landscape that allowed players to feel the tension of a soldier moving through the dark. His work on the original game included the music for every scene except the ending theme.
The Grove School of Music closed its doors in 1991. This event cut short the formal education of Tappi Iwase, who studied there under the American composer Dick Grove. The closure marked the end of an era for many aspiring musicians who had trained at the institution.
The main theme was discontinued because the melody was found to be suspiciously similar to a classical piece by the Russian composer Georgy Sviridov. Konami chose to move forward without the familiar tune starting with Metal Gear Solid 4: Guns of The Patriots. This decision marked a turning point in the franchise's history.
Tappi Iwase made significant contributions to the Suikoden franchise. His work on Suikoden involved creating a diverse array of tracks that ranged from epic battle themes to intimate character moments. The music for Suikoden was an integral part of the storytelling process.
Gigi Meroni scored the cinematic sequences within the original Metal Gear Solid game. This created a distinct separation between the gameplay audio and the narrative cutscenes. The division of labor ensured that the tension remained high during gameplay while the emotional beats of the story were underscored by a different musical voice.