Horizon Air In Favor of E175 over CSeries

First time on here so please be respectful

Horizon Air is starting to take deliveries of more Embraer E175 regional jets. But a thought had occurred to me. Why did they go for the E175 instead of the new CSeries? Considering they have an somewhat large amount of Q400s in their fleet, why didn’t they choose to stick to an “all Bombardier fleet”? Was it delivery slots, cost, maintenance etc? I’m sure Bombardier could have given them a sweet deal and some early delivery slots.

Would they ever consider the E175E2 in the future now that they’ll be operating the EJets?

At most mainline/regional pairs in the US it’s the scope clause, but it looks like Alaska doesn’t have one.

I’d guess it better suits their mission. CS100 is an E195 competitor, not E175.