Because the rubrics for Exposition and Tenebrae conflict with each other; Also the spirit of Tenebrae revolves around the aspect of darkness, particularly the literal darkness that descended at the death of Christ, and the Spiritual darkness that resulted from that dread act while the Redeemer laid in the tomb.

The only candle to remain lit by the end of Tenebrae is the Christ Candle: the uppermost in the hearse; this candle is itself removed (lit) therefrom to the sacristy until the strepitus is made, at which it returns.

This is where rubrics conflict: How can the candles required for Exposition remain lit if all of the candles and other lights in the church, except the Christ Candle, should be extinguished by the end of the Benedictus?

Save the Divine Office, Coram Ssm. for major festivals like Corpus Christi, Christ the King, or Forty Hours; Let Tenebrae be the extreme act of penance and mourning that it is supposed to be.

Salieri,

Tenebrae is usually prayed in the morning, isn't it, when all solemnity of the previous liturgy has been shorn from the altar of repose?

We get a special treat this year. At our parish, we're going to be able to join our clerics for Tenebrae for each day of the Triduum, although I'm informed that (for various reasons) it will be spoken, not sung. Last year, we managed Sung Tenebrae at home, in part because my son who leads a schola at TAC was home (forced home by Shelter-in-Place orders). He and I shared the lion's share of the responsories and the lections, while the rest of the family (the part that still lived here) joined for the psalter.

Tenebrae is usually prayed in the morning, isn't it, when all solemnity of the previous liturgy has been shorn from the altar of repose?

In the 1962 liturgy only, as a matter of rubrics, although this also happens where we must celebrate the traditional rite at much later times due to Holy Thursday and Good Friday being working days. It is usually not possible to celebrate one liturgy after the other, due to the limited resources of a parish schola cantorum, although Ssma Trinità in Rome does in normal years.

Tenebrae can be celebrated on the evening of Spy Wednesday in the cathedral where the newly-invented chrism Mass is celebrated on the morning of Holy Thursday.

Because we are soft the Church allowed us to anticipate this service to the previous evening. The gathering darkness makes the ceremonies more vivid.

Sort of. That is, Matins and Lauds are always prayed together in choir traditionally, even after the reforms of 1911, and even outside of choir, you're expected to pray them together.

So that means that Matins is only anticipated by a few hours when prayed around 9 PM, and then Lauds is anticipated a few hours more, but not a night like those of the Triduum, where basically everyone pulls out the full Gregorian melodies (or even polyphony), Lauds is only anticipated by about six to eight hours, which is not so bad or as absurd as the reformers believed it. Anticipating Lauds was in fact prohibited after 1960, hence the anticipation of Tenebrae is a problem for those following 1962 more strictly. But, you know, I don't really care, so long as people are honest about it.

For my part, I also like having the offices at the same time, or nearly so: 7 PM Tenebrae, then 3 PM for the other offices or something like that.