Where are you? It looks like it could be the west coast? Anyway, it certainly looks dead. Perhaps due to a root rot. The rapid death in midsummer would suggest a root disease, rather than drought (which is typically more gradual).

Also, that root situation looks terrible, with one half perhaps removed and grade changed? Certainly the history of the root zone would help with diagnosis.

Definitely liriodendron tulipfera. The landscaper/yard guy put the mulch touching the trunk which certainly caused root rot. Mulch should be kept at least 2 inches away from the trunk of a tree at all times. Mulch rings are for small ornamental trees and young trees, not for mature shade trees. Never raise the soil significantly around a tree.

I don't agree that the mulch "caused root rot". There is no evidence for this in the scientific literature. It is unlikely, because 1.) Fungi (or oomycetes like Phytophthora cause root-rot), not mulch. 2) Root rot pathogens are rarely capable of colonizing mulch. 3) Transmission of the pathogens from mulch to the host would need to take place through a wound or compromised roots, which could happen, but not obvious here. Again, root-disease could be responsible, but the mulch is unlikely to be involved. The grade changes could be though.

It looks like the bark has rotted away at the root collar, but we can only see the one side. Is the bark like that completely around the trunk? Maybe remove the mulch away from the root collar all around so we can see what it looks like.

Theree's some scale there i think-perhaps Lecanium or another. But your tree is clearly not "dead". Dead trees have no live buds, no green tissues. Yours is not dead.