"Twitter accounts claiming to be located in Iran and throughout the Middle East pushed out many thousands of tweets under a handful of hashtags, such as #HardRevenge and #DeathToAmerica", well, Iran has population of 81 mln people.
I can easily see 'many thousands of tweets' by legit real supporters of Iran regime, considering that Soleimani was considered a war hero. Honestly, for a country with 81 mln population, 'many thousands' does not sound like a lot. It's not even 'tens of thousands'.