Mazda 3 Bumper Damage

So I had a tragic incident and have no idea how.
I got home last night and noticed my bumper was cracked on the front underside. I am guessing I have either hit a kerbstone or a snowbank that iced up. I never heard anything either coz I had the music on too loud.
Anyway I am mad that it happened.
I have called up some body shops to an estimate, some have said that the entire bumper needs to be replaced.
But just wondering what is the plastic part that sticks perpendicularly to the road under the bumper? It is on both sides of the front wheel. Why would the bumper easily crack if something hits that part. See the pictures. Any comments?

The plastic part that wraps around the fender well is called the fender liner.
It likely ripped for a couple different reasons...
- cold weather + plastic = fragile... catching a curb and pulling out will crack whatever part of the bumper is caught.
- the bumper, fender liner, and undercarriage shield are attached together. If you shift one, the rest are going to follow.

To be honest, you could probably find a local joint that'll fix it, but not offer a warranty. Any corporate body shop you go to will definitely replace the cover. They may also be concerned about the actual mounting tabs to the fender (under the headlight).

the way the painted part of the bumper cracked to get it back right you need a new bumper, sorry theres not an easy or attractive looking way around that, i would find a local well reputed body shop and ask how much they would charge to paint a new bumper and change it for you if you dont know how, the fender liner can be reattached usually with new plastic rivets or zipties underneath (as no one who cares what it looks like will see them) if it broke as well new ones are $40-200 depending on year and which one broke. unpainted bumpers are usually $150-400 getting them to paint a new bumper to match your car should only be like $100 maybe $200 AT MOST (just to paint it) and labor just to change a bumper maybe 2-3 hours (whatever the shops rate would be per hour) the newer cars have extremely easy bumpers to remove so if you know how to work on a car you could probably have a new one painted and just put it on yourself, youtube is filled with how tos for this very thing. get a new fender liner or undersheild (if yours is crack and your concerned or just wanna be thorough) and a few new plastic rivets and holders just in case you break some or they are already broken. the dealer should have all those little rivets and plastic nuts and stuff that fit just right for not a whole lot more than the ones at parts stores that may or may not fit well.

While it's not cheap, RealMazdaParts has the OE bumper for about $200. Depending on how you're feeling, you can have the bumper painted and try to replace it yourself, or you can have a shop paint and install it.

the front bumper is extremely easy to replace, had to replace a light assembly and the bumper comes off in under 20 minutes (mainly because so many bolts on the undershield)