Are there any researches that prove that agile testing is better than waterfall?

Hey guys! We are doing agile testing where all crafts are supposed to test. However, got a question from someone in leadership. Why should other crafts do testing when we are not expecting QA to write code or draw? Also they assume it’s cheaper to just hire bunch of QAs instead of waist developer’s time on testing. Are there any researches that prove that doing agile testing is more profitable than doing testing after development?
Thank you!

There are a few in my area, mostly in form of meetups. I’m a member of most of them. Are you looking to grow your community or just searching for online communities to join? There are a lot of MoT meetups that are now online, you could join those.