You are, of course, correct about the relative capacities of the 146-300 and the E195. The difference is really that you could afford to park the former during periods of slack demand given the low capital but relatively high operating costs of the 146. You had to fly the nuts off the 195s to make a high capital cost but low operating cost aircraft work, and if the market demand isn't there to sustain the flying, the economics turn against you pretty quickly.
I suspect if we were to list out all the reasons why Flybe failed, these would be on the list but by no means alone. I am not volunteering to start the list though, nor do I think it is helpful to anyone at this point in time. The Embraer deals were undoubtedly part of the problem and not the solution, but they count amongst many reasons for Flybe's failure.