You’re vastly overestimating the strategic capacity or care of the American voter. Game theory doesn’t fit in a TikTok video.
Mostly because Assad did use chemical weapons and Obama didn't bomb them. Arguably the fact that Obama backed down set the tone for the invasion of Crimea and the Donbas.
Until they were in power of course, and Assad mistakenly assumed the Republican position on this was coherent and actually used chemical weapons again.
Obama certainly didn't bother with as much when offing Al-Awlaki [1]. (An American who took up arms against the United States.)
This was Obama's fuck-up. He was the chief executive and commander in chief. If he couldn't hold the line, he shouldn't have drawn it.
[1] https://en.wikipedia.org/wiki/Killing_of_Abdulrahman_al-Awla...
His supporters absolutely would give a fig about Ukraine if Trump hadn't spent years sabotaging the GOP's historical positions on hostile authoritarians.
How that wasn’t blindingly obvious from the start is a question, but not one he or his supporters actually care about because they couldn’t give a fig about Ukraine. It is entirely instrumental to his personal political advantage in the moment. Being utterly opposed to support for Ukraine was politically advantageous in opposition and supporting Ukraine to the hilt is now politically advantageous in power. That’s all that matters.
Chemical weapons in Syria are an informative parallel. Obama’s commitment to bombing Syria if they used chemical weapons was the worst policy ever from opposition, but actually bombing Syria for using Chemical weapons when they did so as soon as Trump gained power was an obvious necessity.