Mature Apple tree root crown buried

We recently purchased a new acre and with it came a small orchard of six apple trees. We took possession of the home in September but haven't been able to do much until everything finalized last week. Now we've gotten busy poking and prodding. I had obviously noticed the trunks of the apples are very straight, the root crown appears buried. Closer inspection showed us someone placed a border of bricks about two feet from trunk square around it. They are now two or three inches below ground in most places. The trees are mature and could be over 100 years old. The original cabin was from 1905 though I don't think they are unless they've been choked by grass forever?

There have been floods here in 2019, now mitigated through channels which may have caused it but there is also a large field barely uphill that could be sending soil down slowly.  The trees have not been taken care of and the apples were okay tasting, blemished and tiny. One tree I've designated to let become a wildlife habitat and soil nutrients, it has a huge hole and is very unhappy.

I plan to build a large swale north of the trees to catch water but now thinking I may need to build a small one before to stop soil build up on the trunks?

Also, can I dig away this soil around the trunks and remove the bricks or would that cause more harm? My understanding is the crown should be exposed.

Hoping to guild these trees in the future with numerous perennials and plant my shade loving annuals there as well. Any advice always welcome!

**this pic is the front one we're going to take partially down and let a small one grow up.

Melonie -
I would definitely unbury the trunks of the apple trees down to the root crown where the trunks flares out.  The way that they are planted will eventually kill them and there's no harm in removing the soil around the trunk enough to unbury the crown.

We've now done some digging and I'm pretty convinced the history of flooding contributed to how deep the trees are buried. The soil around the base is silty looking and compact, pretty hard to get away. I may have to wait until I can use water to aid the removal, don't want to damage the base with hand tools. For now we've removed the bricks and loosened up the top layers.

I think you're definitely on the right track removing the soil so the root flare is exposed. Several trees in my yard have required that. It is quite tricky to remove the soil without damaging the roots, especially if the soil is compacted. Using water seems like a good possible option. Another option if that doesn't work is an air spade. It uses an air compressor to remove soil without damaging the roots. I believe you can rent them or find an arborist with one.