Don’t know why he is doing it but I predict that his brief Connection to the Stormfather will help him bring the SF Spren into the Physical Realm, where he will die (not necessarily at Ishar’s hands).
With Honor’s last splinter destroyed, Honor’s shard can finally be taken up by a willing vessel - queue Dalinar.
This is foreshadowed by Dalinar (not the Stormfather) accepting Kaladin’s Words for the 4th Ideal.