PubSub doesn't support qos 1. But this doesn't seem to be a problem, if I flush the tcp channel. The mqtt connection time is still at 1s 800ms. At least the publishing is now a lot faster.
17:13:23.376 -> start
17:13:23.509 -> bme650 data read in
17:13:23.650 -> Wifi connected
17:13:25.461 -> connected mqtt
17:13:25.461 -> publish mqtt
17:13:25.481 -> flushed mqtt
17:13:25.508 -> stop