"Oh no, my tires are going flat! I'm not going to be able to win this race!"

Here, we have Rarity look down in horror at her skates to find all 8 tires went flat during the skating part of the Tri-Cross Relay.

It turned out that an Aridaginatan temporal agent (hidden among the audience, disguised as human) from the distant future (the year 2399), who had time traveled to the 21st century, had planted those thumbtacks to alter the Friendship Games (and the rest of the EQG timeline) in an attempt to erase the Federation from the timeline.

Because of this, Rarity never boosted Pinkie Pie to the finish line. Resulting in Sunset and Rainbow Dash also losing, Sugarcoat's death via plant monster, and CHS losing the Friendship Games. As a result, students became demoralized to the point that they never fundraised to visit Camp Everfree. And as a result, the camp closes. The Mane 7 never participate in the dance video competition (since Camp Everfree was eliminated from their motives), resulting in them never visiting the Daring Do movie. This in turn caused Juniper Montage to successfully get the movie cancelled. Starlight still visited the human realm, but because the events were altered, she finds it boring and returned to Equestria the same day (due to never meeting Juniper Montage and stopping her rampage). As a result, life became depressing for the Mane 7 to the point Sunset wasn't prepared for Wallflower Blush's memory stone fiasco. As a result, Wallflower wins, and Sunset is alone forever (with only Trixie as her friend). The rest of the digital series do not happen. Life soon became more depressing for Sunset, resulting in her commiting suicide in 2023 while babysitting a 10-year old Zefram Cochrane at his aunt's house in Canterlot City. Zefram got so traumatized by his babysitter's death that he grew up differently to the point he never invented warp drive in 2063 (which in turn, the Vulcans never came and the Federation never exists).

However, the Aridaginatan's plans were thwarted by Captain Shoichet of the USS Sunset Shimmer, Captain Braxton of the USS Relativity, and Temporal Agent Daniels. Daniels then removed the thumbtacks, causing the Friendship Games to go back to normal.

This vector is from the Star Trek: Sunset Shimmer episode "Temporal Tri-Cross Crisis, Part 1" (Season 5 Episode 14)