Nothing wrong with Swinson - As a junior party in a coalition it is easy to cop for all the fall out but in reality they would have been a moderating force, we will never know how much worse it would have been if Cameron had an outright majority.
The reality is that Corbyn / Johnson are divisive toxic leaders who play to the base while demanding loyalty from the moderates on whose votes they are reliant on to ever win an election. They are both terrible leaders. The SNP don't have any moderates as there whole mission is a single extreme populist proposition. In comparison Swnison is on a different level as she isn't toxic/divisive in any way, they are the opposite broadening their appeal and that is why the Lib Dems are on the up big time.