Force prescience is a tricky thing (as an example, see Luke seeing Mara Jade lying dead looking in a pool of watersomeone's death the wrong way in Spectre of the Past/Vision of the Future): (spoiler alert):
He had a Force Vision that showed Mara Jade looking dead, in a pool of water. That vision drove a lot of his decisions/behavior in those two books
...
TWIST! She ended up lying in a pool of water but survived in the end of the second book.
It's quite possible to see one possibility shown to you by the Force, and to interpret it WAY, WAY incorrectly.
Clouded the future is, young Padawan. Always in motion.
