Kasich voters were the most doggedly committed anti-Trump voters and very few of Kasich's ~10% of Republicans go to Trump.
While that was true in the latter half of the race, it was less so earlier on. Kasich and Trump actually had a fair bit of overlap in the early states as both appealed to moderate voters. I myself was a Kasich/Trump supporter; if Kasich had dropped out early on, I would have supported Trump in the primaries.
Kasich and Trump were the two candidates I preferred in 2016 as well.
