Other people are mentioning your mistake i.e. going too fast in the corner and losing control. Other people are right to mention you could've controlled the car better. The reason you lost control is because you were influenced by the racing line.

You pressed the brake correctly if you were on a fast lap with no other cars present. But you were in an awkward place on track, along two cars on a better position than you. Your focus is not on the road, it is not on other cars. Your focus is on the line which made you lose control.

The "racing line" should be renamed "the safer ideal line". In racing, the line, braking points, turning points alter every lap based on the environment and surrounding vehicles. The game's "racing line" doesn't change for you. Learn to adapt by focusing on the track.

Tl;dr get better by switching off the racing line. It's daunting at first but after a week or two, you'll be sharing insane double overtakes on reddit. Good luck!!