There's been a long-standing/known issue around the delay that exists each time a lead or set of leads are imported into Marketo - whether it's a list import to manually adding them individually (which we do on occasion as we test new customizations). Here's an existing thread that discusses these issues: Re: List import of members taking significantly longer for them to be available to smart campaigns
Today, this issue is also making it so that the lead(s) do not show up in any smart lists - or are available in searches in the specific lead partitions (e.g., if the lead was routed once it was imported based on country). As an FYI, Marketo was able to replicate this and posted an alert on the Support portal:
P1 Alert - Customers may experience delays in Smart Lists or Static List imports
Customers may experience delays when importing static lists or compiling smart lists. We are investigating this now and will post updates as soon as they become available. If you have any questions, please contact Marketo Customer Support https://support.marketo.com.