Why is Rito releasing so many champs that can troll their teammates?

...They aren't?

• Tahm has 2 skills that could theoretically troll teammates: his W and R. However, the ally can exit his W ANYTIME they want to, and his R pings the spot he has chosen before he can even let allies in, and even then allies can choose whether or not to go in.
• Ekko has... his R I guess for leaving a fight and accidentally baiting his team, but literally any champion with an escape can do that already.
• Bard probably has the highest potential trolling, as his E can provide enemies a path to take and his R can stasis allies, but both of those features also raise his skillcap and plays he can make extremely high. Even then, not very high troll potential.
• Rek'Sai has...nothing other than intentional feeding/calling teammate locations/etc., which every champion can do.
• Kalista has her R, which can move a support from where they wanted to be, but also provides a long range dash + knock up alleviating almost any problems (other than using it at max range when your support was about to catch someone).
• Azir has nothing.
• Gnar has nothing.
• Braum has nothing.

Let's uh, skip this massive list of "nothing" and go to actual ones.

• Thresh has his W, but you can choose when to take it.
• Volibear (and Vayne, and Skarner, and Singed, and Blitzcrank, and literally every champion with a pull/knock back/drag) could throw a tank into your face or throw a carry at you when you are low health.
• Jarvan 4 (and Trundle, and Anivia) can wall you in with an enemy or block off a path you were taking.

So of the "new champions" most of them have trolling potential equal to a Thresh at best. All of the pull/knock back/drag and the terrain creating champions are around equal to Bard in terms of trolling.

As a reminder, player skill and temperament has a higher effect on "trolling" with champions than trolls do. If someone wants to troll they can already do so by constant intentional feeding or other such acts no matter the champion.

like bard and ekko

Any champion can be used to "troll", so this is not an issue in any way.