It's not an unreasonable assumption either. Nick Clegg did seemingly get rewarded for tanking the lib Dems. The ones lower in the party hierarchy will also have seen plenty of examples of pyrrhic loyalty being rewarded.
What modern parties effectively teach - UK Labour is just one of many examples, not even the only example in the UK - is that the supreme political virtue is loyalty to decisions taken in rooms you weren't invited to. That, they think, will eventually get them invited to those rooms.
The sad thing is that whether the rooms actually exist or not, the result is much the same.
"Don't obey in advance" is Tim Snyder's first rule against tyranny. While that is a great moral rule to follow in tyrannies, all organizations want people to obey beforehand, whether tyrannies or not. It's called showing initiative, doing what's needed without having to be told explicitly, and no organisation can function without it.
But in organizations with opaque power structures, where it's expected that decisions are taken unaccountably ("Noen har snakket sammen", loosely, "There has been discussion", used to be an ironic phrase in the Norwegian Labour Party), people may easily slip into obeying in advance a tyrant who doesn't even exist. They're trying to please the responsible people who are surely in charge somewhere nebulously above them in the hierarchy, but those people don't exist, it's bullshitters like Starmer all the way to the top.
Snyder's had his first rule, but I have a first rule too, which I keep repeating, and that is that powerful people believe in all the stupid things regular people believe in. They just act differently on the beliefs. A common person who thinks covid was an ethnically targeted bioweapon rants about it online and gets banned from Reddit. A powerful person who believes it, thinks "it's important that we too get such a weapon, and don't trust experts who say it can't be done, they probably just have scruples". A common person who thinks a Jewish cabal rules the world maybe pesters his relatives with it all day. A powerful person who believes it - well, he's more likely to do something like what Starmer has been doing the last decade. You don't try to fight Bilderberg, obviously, you try to get invited to it. Once you do, (like e.g Jens Stoltenberg was) you probably get disappointed and try to figure out who the real competent ones behind them too are, and how to join them - but you're not terribly disappointed, because on the way up you've been rewarded by all the others who thought they'd be rewarded for supporting someone like you.