Probably because he hit .250/.310/.325 in 352 PA at Portland in 2019 and everyone in the world was like "yeah, he's not going anywhere without any power."
Are people familiar with Jarren Duran's minor league track record? I'm guessing no if people are seriously asking why he felt the need to retool his swing.
In 2018, he had a .421 BAbip, 6.5% BB%, 15.5% K% and a .159 IS0 as a 21 year on in Rookie League and A ball.
In 2019, he had a .480 BAbip, 10.2% BB%, 19.5% K% and a .156 ISO as a 22 year old in A+.
In 2019, he had a .335 BAbip, 6.5% BB%, 23.9% K%, and a .075 IS0 as a 22 year old in AA.
It was completely predictable that Duran would completely wash out without revamping his game.
In 2021, he had a .288 BAbip, 10.6% BB%, 23.3% K and a .258 ISO. He went from being written off to a top 100 prospect.
And even if the team told him theh wanted a high OBP, defensive OF who steals bases, it doesn't mean he can just do all that stuff. It would be great if it were as easy as "Hey Jarren, get on base 38% of the time and play GG defense. Also, steal 50 bases." But alas, it is not.
Maybe Jarren Duran isn't good and is one in a very long line of failed prospects.