What did I do wrong?

What did I do wrong?

I have a big area of dirt off my main courtyard that my bedroom and studio windows face into. It's walled in on 3 sides and covered by a patio with shadecloth. It gets a little bit of sun, is sheltered from the wind but still gets rain. A few months ago I planted a few plants which are doing ok, with the exception of the groundcover plants and a fern which have died, and put down some mulch. Now for some reason the mulch and some of the top layer of soil is very hard and sort of stuck together like a crust. Any ideas why this might be? We had a very hot summer but we've finally got some rain in the last couple of weeks. Did I let it dry out too much? How can I fix this and make it so that plants will want to grow there? And how can I stop it from happening again? I can't imagine that crust would make it very easy for the plants to grow and spread. I have already broken it all up with a shovel and rake and given it a good watering. Apologies if this is a silly question but I'm new to gardening as I bought my first house 6 months ago and didn't see the point in gardening when I was renting. I live in Perth, Western Australia if that helps!
Welcome to My Apartment

Welcome to My Apartment

My Living Room and Desk Area

My Living Room and Desk Area

Mutant coleus

Mutant coleus

Large scale composting

Large scale composting

new room!

new room!

we have a lot of toys

we have a lot of toys