It meant van Garderen's chase back to the peloton was disrupted, and he ultimately crossed the line 54 seconds later - initially being ruled to have tumbled to 13th overall, 47 seconds off the lead. The second placed rider, Gianni Moscon, was caught up in the crash as well, and also initially plummeted out of the top 10.
Bennett somehow managed to get back into good position in the peloton to avoid the final crash, and eventually manoeuvred himself to 17th place on the stage won by Fabio Jakobsen. It looked as if he had jumped into sixth overall - just 29 seconds off the lead, and right back in contention for the overall title.
However, the race officials then changed their ruling due to the crashes, giving the riders all the same time - a huge reprieve for van Garderen, who remains in the lead of the race, and an unfortunate result for Bennett, who remains in 10th, 36 seconds behind.
With van Garderen seeming to have lost time, it would have put Bennett right amongst the favourites ahead of the penultimate and likely deciding stage - which finishes with a 7.6 kilometre climb up Mount Baldy at an average gradient of 8.8 per cent.
However, now he remains 36 seconds behind van Garderen, one of the best climbers at American altitude - a much harder gap to bridge than the 20 seconds to the next-best placed overall contender, Tadej Pogacar.
So, instead of being in sixth overall, and right back in the mix for a second Tour of California title, Bennett instead is still slightly off the pace, and will need to produce something special on Mount Baldy.
The riders will all still have to get through a tricky stage five tomorrow though, featuring a 900 metre kick at nine per cent with six kilometres to go, and as today showed, you can't switch off for a second if you want to win the Tour of California.
(Well, actually, maybe you can - but only if the race officials are feeling generous.)
Bennett will need a bit of luck though, and after the drama today, maybe he deserves it.
