At the start of the "Avengers: Infinity War" movie:
Thanos and the Black Order have boarded the Asgardian ship, killed most of the inhabitants and beaten Thor and Hulk.
Then:
A wounded Heimdall teleports Hulk / Bruce to Earth for safety before Thanos kill him.
Why:
Didn't Heimdall teleport Thor instead? Isn't Heimdall more responsible for Thor than Hulk?
Based on my admittedly limited understanding of ancient Norse culture, and allowing for movie exaggeration, it is possible that the Asgardians had a particular responsibility to protect Bruce because he was a guest.
In any case, Thor would not willingly abandon his people, and Heimdall knew that. He may also have
seen that help was coming and realized that Thor would need to reach Nidavellir, which would have been hard to do from Earth,
and/or
anticipated the upcoming attack on Earth,
but even if he didn't, I think the Sacred Hospitality trope, combined with Going Down with the Ship is probably enough to explain his decision. (Warning: TV Tropes links.)
This is totally based on what I think,
What I think is that Heimdall knew that Thor could survive being in outer space until the guardians came (because he probably saw that the guardians were on their way) and that hulk being beaten up he might have assumed that the hulk may turn back to Bruce Banner and might not have a chance in surviving in space and also Bruce could find the avengers more easily than Thor as he is from earth (As the avengers are broken up and Bruce has a better chance in locating them than Thor, heimdall probably knew that the avengers were disbanded).
This may be wrong, but there is the simple fact that Bruce was not restrained, while Thor was restrained in metal. Perhaps his transporting ability can't pull people out of constraints. In this case the constraints were magical, even! The transporting beam seemed to make a hole through the ship to transport Bruce, but I don't know if it could tear Thor safely out of the metal.
I like the theory that hulk was a guest therefore heimdall might have teleported him for the sake of honor.. But i also think (its a stretch) that since heimdall had the power of sight, both past and future, that perhaps he could see something in banners future that was not hinted on in the movie. Similar to how dr. Strange saved tony from certain death by giving up the time stone in the particular way he did.. Ie bargain to save tonys life by giving up the stone (14+ million future outlooks and only one in which they win against thanos) clearly.. Tony is key to the 1 possible future that they win the fight. I digress..anyhow. I think heimdalls choice to save banner was the same.. He knew the future and that banner or hulk was a key figure in defeating thanos.
