Thunar is displayed with Atril's theme in i3

Inside i3wm,

After running and closing Atril (MATE app), and then opening Thunar (XFCE app) it(Thunar) is displayed with MATE’s theme.

If Atril is not executed beforehand, Thunar displays no change in the theme.

Why does this happens?

they are both gtk … but maybe one usurps the other, such as by having a later version?

I have tested all these MATE apps: pluma, caja, mate-terminal, mate-calc, eom, engrampa.
And none of those altered thunar’s theme. I believe it is an atril’s specific bug.