If Asgard wasn’t destroyed do you think thanos would have invaded Asgard or he would've planned an invasion
If that was needed to do, he would do it.
What's the question? Both options are the same thing
He would’ve invaded Asgard. especially if he grabbed the power stone first from Xandar. He could’ve assimilated the planet instead of Surtur.
His army of outriders or the black order could not withstand the power of Loki Valkyrie Thor heimdall and many more so he would probably have to do it himself.
What do you think?