In Sweden, the executive power is vested in the Government (i.e. The country's "Cabinet" which consists of the Prime Minister and other Ministers), as opposed to the Prime Minister.
This means that the Prime Minister (at least in theory) can only take political action if a majority of the Government members approve the decision. If the Government does not approve a decision, the Prime Minister is expected to not act on it.
However, there doesn't seem to be any ramification if the Prime Minister chooses to lead the Government with an iron fist.
If a majority of the Government members oppose a decision, the Prime Minister can very well overrule everyone by threatening to dismissed them. This of course would happen entirely behind closed doors as Government meeting records are kept secret from public.
In the absence of obvious ramifications to incentivize the desired behavior, why would the Swedish Prime Minister act in accordance with the Government's collective will?