Progress that fast

Looking at the Cup standings, I see clubs of level 5, with average player level well over 50, with team value several hundreds of thousands, but with players' ages 19-20 and such.

How they do that? by investing hundreds of real dollars in personal trainers? or there's some technique?

At level 5 you have scouts After 45Q, so they probably are token buyers that buy young fast trainer with 44Q or near and power train them.
A fast trainer at level 5 with 18 YO 5* has a MV above 10M.