I would say, rather, by early April both Seward & Lincoln thought resupplying Fort Sumter realistically might result in a Confederate attack, or it might not, but the alternative was abject surrender and neither could accept that, politically, if for no other reasons.
I suspect Lincoln understood just as well as Jefferson Davis did that any Union response to battle at Fort Sumter, no matter how minor, would instantly flip Virginia from Union to Confederate.
So Lincoln must therefore have believed Virginia was effectively lost anyway and any conceivable alternatives would produce even worse results.
Plus he thought the Fox mission had a good chance of success which would purchase several more months to deal with other issues.
If by early April Seward's views still significantly differed from Lincoln's, we don't know of it.
Just my opinions...
Respecting the wishes of a state that you should leave is "abject surrender"? I hope you never have any unwelcome house guests.
I suspect Lincoln understood just as well as Jefferson Davis did that any Union response to battle at Fort Sumter, no matter how minor, would instantly flip Virginia from Union to Confederate. So Lincoln must therefore have believed Virginia was effectively lost anyway and any conceivable alternatives would produce even worse results.
I've read an account of Virginia officials meeting with Lincoln to offer him the assurances that he sought regarding Virginia remaining in the Union if he removed the garrison from Sumter.
He responded to the effect of "Too D@mn late sir! You are too late!"
If by early April Seward's views still significantly differed from Lincoln's, we don't know of it.
One doesn't continue to disagree with the boss and stay employed for very long.