The truth is that France did have less incentive to prevent crossings as there was no longer any financial aid for them doing so. To be clear: the UK would definitely not act differently in that situation; though it's reprehensible.
It's also true that France no longer has infrastructure to cope with it's own migration and tougher laws being introduced in French are pushing migrants to tackle the treacherous journey.
However since the deal has been reached France is doing as much as it can to prevent crossings -- that said, it betrays the real problem.
The number of "small boats" making crossings ("Small Boats" being a parroted line) was 29,090 for the year of 2023 (as of December). Which is a reduction from the year prior due to our agreement with France. But that's nothing compared to the net migration figures of 750,000 (largest on record and by a huge margin) and that also precludes the fact that of those migrants crossing on small boats may not be granted asylum (5,284 as of September '23 - 18%) were denied and sent away.
Not exactly an embarrassingly large number in the grand scheme of things, which makes it a bit of a boogeyman.