Training ups Level of Driver, but end of the race, it downgrades a level

I've been racing and noticing this for a little while now, but when I train both my drivers, the blue bar moves up, and for one driver, ups the level. However on race finish the level is back down to what is was previous to the training. Any ideas why, even when I get a 1-2 finish?

Probably driver stats atrophy. The Overall Level is an average of sorts of the individual statistics (Aggression, Talent, Focus and the like). These stats go down a bit each race, so if your training raises the average just enough to reach a higher level, the atrophy from the race will reduce the average enough to drop back down. Like going up to Level 5.02 (displayed as Level 5) with training, and then the atrophy takes the driver back down to Level 4.98 (displayed as Level 4).

^This. Exactly this.

Your drivers are 33 and 35 years old. They will atrophy quite a bit compared to a young driver which in return lowers your level faster than a younger driver.

Thank you, looks like new drivers at the end of the season

Buy them as young as possible, Asher!