"&" and "|" vs "and" and "or" for "AND" and "OR" operators in Django

Your test data is quite insufficient for this test since both rows contain popular. (IOW, anything that would find popular is equivalent to Blog.objects.all().)

Anyway, boolean or and and don't work correctly here (since they're just doing boolean evaluation), but you're just not noticing because of the above.
You need to use the "bitwise" | / & / ^ operators, as documented. ("bitwise" in quotes, since the Q class overloads the operators to not be bitwise at all.)

For proof, let's look at the Qs in isolation, without querying anything...

>>> from django.db.models import Q
>>> pop = Q(post__contains="popular")
<Q: (AND: ('post__contains', 'popular'))>
>>> sim = Q(post__contains="simple")
<Q: (AND: ('post__contains', 'simple'))>
>>> pop and sim
<Q: (AND: ('post__contains', 'simple'))>
# ^ incorrect; evaluates to `sim`
>>> pop & sim
<Q: (AND: ('post__contains', 'popular'), ('post__contains', 'simple'))>
# ^ correct: combines the two q:s with `and`
>>> pop or sim
<Q: (AND: ('post__contains', 'popular'))>
# ^ incorrect; evaluates to `pop`
>>> pop | sim
<Q: (OR: ('post__contains', 'popular'), ('post__contains', 'simple'))>
# ^ correct: combines the two q:s with `or`

When running the filter() code using & or Q() and & or using and or Q() and and in test() view as shown below:

# "store/views.py"

from .models import Blog
from django.db.models import Q
from django.http import HttpResponse

def test(request):

    # With "&"
                                                     # ↓ Here
    qs = Blog.objects.filter(post__contains="popular") & \
         Blog.objects.filter(post__contains="simple")
    print(qs)

    # With "Q()" and "&"
                           # ↓ Here                    # ↓ Here
    qs = Blog.objects.filter(Q(post__contains="popular") & 
            　　　　　　　　　　Q(post__contains="simple"))
    print(qs)              # ↑ Here

    # With "and"
                                                      # ↓ Here
    qs = Blog.objects.filter(post__contains="popular") and \
         Blog.objects.filter(post__contains="simple")
    print(qs)

    # With "Q()" and "and"
                           # ↓ Here                     # ↓ Here
    qs = Blog.objects.filter(Q(post__contains="popular") and 
            　　　　　　　　　　Q(post__contains="simple"))
    print(qs)              # ↑ Here

    return HttpResponse("Test")

& or Q() and & can run AND operators according to the query logs of PostgreSQL as shown below. *You can check on PostgreSQL, how to log queries with transaction queries such as "BEGIN" and "COMMIT":

And, when running the filter() code using | or Q() and | or using or or Q() and or in test() view as shown below:

# "store/views.py"

from .models import Blog
from django.db.models import Q
from django.http import HttpResponse

def test(request):

    # With "|"
                                                     # ↓ Here
    qs = Blog.objects.filter(post__contains="popular") | \
         Blog.objects.filter(post__contains="simple")
    print(qs)

    # With "Q()" and "|"
                           # ↓ Here                    # ↓ Here
    qs = Blog.objects.filter(Q(post__contains="popular") | 
                             Q(post__contains="simple"))
    print(qs)              # ↑ Here

    # With "or"
                                                     # ↓ Here
    qs = Blog.objects.filter(post__contains="popular") or \
         Blog.objects.filter(post__contains="simple")
    print(qs)

    # With "Q()" and "or"
                           # ↓ Here                    # ↓ Here
    qs = Blog.objects.filter(Q(post__contains="popular") or 
                             Q(post__contains="simple"))
    print(qs)              # ↑ Here

    return HttpResponse("Test")

| or Q() and | can run OR operators according to the query logs of PostgreSQL as shown below: