why do they feel like they have to compete with current times and try to be mainstream?

Aerosmith, Prince, Santana, David Bowie and The Rolling Stones (just to name a few) all have done it, with some concepts doing well and some not.

but why would they change their music so drastically just for a little exposure?

maybe somebody can explain it to me because i don't get it

Wider audience, BIGGER money and like you said, exposure.

Nothing's wrong with that though, its the way of the business.

They could just be inspired by a recent release or movement. I know Chris Jasper has said that he was very inspired by Stevie Wonder, which explains a lot of the 3+3 Isley Brothers material.