Why did Trump say we should be in alliance with Assad and Iran?

[Rules for me, but not for thee]

Why not? Defeat ISIS and deal with the differences after, hopefully diplomatically.  I agree with Trump - I rather be friends with Russia or Iran than the last 30-50 years of hostility that hasn't got us anything but more enemies.

Also it's not a full alliance: it's just an alliance against a common enemy.  Once that's cleaned up, work on the future of trade and friendship and not further military alliances.

[Rules for me, but not for thee]

Because they are killing ISIS and we should be as well

Even if that was true, trump also said the Iran deal was a terrible idea, that consistency from him

That deal was done and Iran has already used the money it got through that deal to become a regional power. Nothing can be done about it any more. We need to accept the new reality that we have to work with Iran too.

This^^ It was a bad deal.  I think we could've did better, but it is after the fact now.