the Trinity in Isaiah

Isaiah 48:12-16

12 “ Listen to Me, O Jacob,
And Israel, My called:
I am He, I am the First,
I am also the Last.
13 Indeed My hand has laid the foundation of the earth,
And My right hand has stretched out the heavens;
When I call to them,
They stand up together.
14 “ All of you, assemble yourselves, and hear!
Who among them has declared these things?
The LORD loves him;
He shall do His pleasure on Babylon,
And His arm shall be against the Chaldeans.
15 I, even I, have spoken;
Yes, I have called him,
I have brought him, and his way will prosper.
16 “ Come near to Me, hear this:
I have not spoken in secret from the beginning;
From the time that it was, I was there.
And now the Lord GOD and His Spirit
Have sent Me.”
17 Thus says the LORD, your Redeemer,
The Holy One of Israel:

“ I am the LORD your God,
Who teaches you to profit,
Who leads you by the way you should go.
18 Oh, that you had heeded My commandments!
Then your peace would have been like a river,
And your righteousness like the waves of the sea.

Who's speaking? "I am the first, I am also the last." That's obviously God.

"From the time that it was, I was there. And now the Lord GOD and His Spirit Have[a] sent Me.”

The revelation that underlies our understanding we label "the Trinity" didn't originate in the 1st century.