That's because they're two separate continuities. Even though Marvel did an adaptation of the animated movie, and Galvatron was always considered to be an alternate future version of Megatron, the Marvel continuity completely ignores the animated continuity with very few exceptions. Characters in the comics took damage more regularly, and the majority who did get killed were mainly destroyed by Starscream with the Underbase power (which is essentially the power cosmic).
The UK comics get even more confusing when it comes to continuity because they have a whole range of exclusive extra filler. They were printed weekly where the American edition only occurred monthly, and issues that were back to back in the American run were sometimes spread apart by several issues in the UK. So they basically had to invent a lot of stuff to cover the time between the American issues being reprinted. Oftentimes small edits where made to reflect changes in the respective continuities. Thus Bumblebee's evolution into Goldbug has two different takes in the comics, and a third in the cartoon.
Confused yet?
Oddly enough, in the very early draft of the animated movie, Thundercracker and Skywarp are clearly implied to be casualties in the assault on Autobot City (Thundercracker gets cut in half by Bluestreak with a sword), yet later they are named as part of Shockwave's defense forces when Unicron attacks Cybertron. And they get killed again fighting Unicron.
The UK stuff was infinitely better than the US stories. Bud Budiansky or whatever his name was was a pretty silly writer (wrestling micromasters? please).
Target 2006 and Time Wars blew anything the US wrote out of the water. Hell, the US eventually pinched the Great Furman because of it.
I find it amazing to hear about stuff from the movie that never happened, like Red Alert being shot in the back by the Constructicons, or Unicron using 'mist' to dissolve planets rather than eating them (although the version we got was way cooler
).
