Addressing the club's postseason outlook, Tomkins highlighted the pressure on St Helens to maintain their playoff streak.
"Saints wouldn't expect to be sat down in sixth after 20 weeks of the season.
They've also got a really tough run-in to the end of the year, and I think this sounds like the club have gone 'look, we're borderline here'," he said.
He concluded that the hierarchy made the prompt change in hopes of sparking an immediate turnaround on the field.
"This is a side that has always made the play-offs. Never once have they missed the play-offs.
They sit in sixth, and there is a chance they could slip out of there," said Tomkins.
The pundit added that the decision aims to shift the team's trajectory before the regular season concludes.
"St Helens have gone 'look, we make a decision now that we go in a different direction, and hope that the players react to that and performance on the field changes'," said Tomkins.
Interim manager O'Carroll, a former Ireland international, previously coached Newcastle Thunder and Bradford Bulls.
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He is set to leave St Helens at the end of the season to move into rugby union, while the club considers long-term candidates for 2027.
