Speculation which I made clear.
I think you just made this up.
:-} Certainly not out of whole cloth. It is simply my hypothesis on why such a smart scientist developed a theory on general relativity and then wouldn't go where the theory, and his equations, took him.
Einsteins papers and other writings indicate that he wanted a solution that was static.
Yeah, I've said that about ten times up thread but it never hurts to repeat it. The problem is that general relativity did not take him there. He fit the science to his a priori assumptions. My question is why? You got an answer, I'd love to hear it.
After discussions with Hubble, Einstein accepted an expanding universe.
Right, which doesn't answer the question of why he modified his theory to fit his a priori assumptions.
The constant comes from the solution to a differential equation. You have to go with what you have to assign a value to it. Until you know better, you only have what you have to work with.
The static universe was also Newton's assumption and most people's until Hubble. Einstein introduced the cosmological constant to agree with the then-accepted theories. After discussions with Hubble (much later), Einstein changed his mind. You could have just looked these things up; they are not secret nor particularly hard to get.