From first approximation, there are 2 major questions to initiating a conflict.
1. Will I be able to stay in power? (Related: Will my populace support this war? Will my economy keep functioning?)
2. Will I end the conflict with more power / prestige / resources? (Related: How expensive will the conflict be in blood and treasure?)
Most of the things the West are doing over Ukraine are to make the "Related" answers less palatable. Very few people are calculating enough to climb to power, then risk everything on a gamble with bad odds.
If China gets serious about Kinmen and Matsu, then everyone should start worrying.