There were 2 major reasons for capturing Saddam:
- Possessing WMDs (Never proved completely)
- Killing Shias by Chemical Weapons
In the neighbourhood of same Iraq, Bashar Al Assad has been doing exactly the same to Sunni/Christians by using both Chemical Weapons and Barrel bombs (which are banned by UN - correct me if wrong).
On the other hand, US proclaims it is Anti-Assad and all that crap, so why it has spared Assad to date and Saddam was captured?
NOTE
I would appreciate if there would be some research before posting an answer. Those who are still living in ISIS hoax are suggested to read following three articles, two by Kenneth Roth (Ex Director, Human Rights Watch) and one by Dr. Annie Sparrow of Mount Sinai Hospital
- Syria: What Chance to Stop the Slaughter?
- Barrel Bombs, not ISIS are major threat
- The Ethical Cleansing of OCHA in Syria
UPDATE
Many commentators and couple of answers have pointed out the change in regime in US and Obama following a different policy to Bush, but under the same president, there has been an invasion in Libya. Needless to mention their Drone policy
There has been an invasion in Libya
If there are no troops, there is no invasion... Really, you are not asking a question but making an statement and modifying it when you do not like the answers.