Well it actually doesn't make sense because the most logical thing would be to have Jiren possibly wipeout everyone which he could more or less do and end up winning the tournament. However, Dragon Ball has always been a "Macho, power" based show and the most logical explanation as of now is that Jiren is only interested in fighting someone who is worth is time and is not interested in fighting anyone weak.
I think the only possible shot Universe 11 have to win the tournament is by the sheer intimidation of Jiren's power. Dyspo is possibly on the same level as Mid-tier fighters like say Android 17 or Gohan and possibly even weaker but is no way strong enough to face some of the high tier characters like Vegeta and Golden freiza unless he manages to utilise his speed and counter their power. Toppo, on the other hand is a lot more powerful and we see him push Goku into using kaioken and Toppo was suppressed and wasn't fighting at full power. So ideally speaking, Toppo is strong enough to take out most of the fighters but might have trouble with the other high tier characters like Vegeta and Freiza. We have seen someone like Kale being able to rattle the whole stadium when she released her ki and also knocking out a few fighters in the process. So even if toppo and dyspo were to be eliminated, Jiren could possibly unleash his god of destruction level energy which is undoubtedly strong enough to wipe out every fighter there except (UI Goku).
Even after toppo fought goku during the Zen exhibition match and Vermouth asked him whether he could defeat goku; He responded that he wasn't sure and if he were to fall, Jiren would still be there. I think Universe 11's strategy would be, to take out as many fighters as possible and even if they were to fall, there isn't anyone capable of taking out Jiren or even strong enough to put up a decent fight.