(The Avengers were on break and they didn't notice Thanos show up very mad because the Avengers are still alive,cause he knows he can't accomplish his dark plan with The Avengers and The Guardians of the Galaxy alive cause he knows they would try to stop him)
Thanos: This is a big mistake! I should have destroyed them earlier.........
(He knows about The Avengers because he knows they are powerful.......And his scared they could team up with the Guardians of The Galaxy because he knows they're unstoppable,that's why he wants The Avengers dead! So that he can easily defeat The Guardians of The Galaxy And Continue his Dark plan...)
After the day that happened Shield received a message from The Guardians of The Galaxy and asked to help them destroy Thanos
Nick Fury: Looks like I need to Assemble them again...!