Before he died Lincoln came up with the idea of allowing the southern states to come back into the Union if 10% of their population pledged their loyalty to the Union. This system would allow for them to quickly be admitted back into the Union with minimal conflict. When Lincoln died and Johnson took over, the radical Republicans in Congress took over the process and implemented policies to make the South pay for leaving the Union.
The us constitution calls seccession as treason. Treason is punished by death. The job of the president is to enforce the constitution and sup court interprets constitutions and congress takes taxpayers money and lobbyist money that is thrice as much...clear?
He wanted to put them back in the union and preserve the union. After Lincoln's assignation radical republicans kept president Johnson from fixing the union, the republicans wanted to really rub in the victory to southerners and keep the old states as territories
He came up with a plan to help them recover- I forget the name of it. But he didn't treat the south bad or anything. He died before he could really do anything, though