Quick question:
What ISP event are you talking about? You said something about WHOBO, but I can only remember the first WHOBO running ISP. If that's the event you are talking about, then I'd like to personally dispute your claim that most people secretly liked ISP.
I was at WHOBO. IIRC, we only did Doubles ISP and not Singles due to how long the tournament was running, and 1 V 1 ISP was not going to start until Sunday. In fact, I think Doubles ISP was literally the first event going on for the entire tournament. I teamed up with a good Buddy of mine (We got third place, team name "We abuse the Homeless")
We played a lot of strong teams, and only lost to the people who got 1st and 2nd. M2K and Inui won the event. Lee Martin + his partner (I want to say UTD Zac but I may be wrong) got second.
I know that ISP has probably been refined and tweaked a lot over the years, but on that day when we played, people did not enjoy the rules. The item list was obviously tweaked to turn off some of the more obnoxious items, however there was one exception that was probably the most unpopular idea they had. Smashballs were legal, HOWEVER each team was limited to one. I don't recall if it was one Smashball per game, or per set, but there was a limit in place. Items were put on Medium I believe, and Smashballs spawned a bit. It was a big enough deal, that in our match vs Mikehaze and his partner, we had already reached the Smashball limit and were required to not obstruct them from obtaining a Final Smash. That's right: we actually had to move to the other side of the stage and wait for Mike to smack it enough times to break open.
Later on in the day, in losers bracket about to play for 3rd place, the other team came up to us and asked if we would be fine with turning items completely off to do regular doubles instead. They arguably lost to a weaker team due to items, and they did not seem inclined to have a repeat of bad luck. Our side agreed to this, and we played on livestream without items. It was a bit ironic, because the team we chose to fight them was Diddy + Peach, and we ended up throwing a lot of stuff regardless when they went Double MK. After that match, we found out later that other teams had agreed to matches with no items near the top 8ish spots in bracket.
In the end, no "bad" team got a top 5 placing due to lucky items or whatever. However, I will say that the response from the players we met in bracket, and from talking to people afterwards, was not very positive. Not many people were looking to prove a point or enter for bragging rights on how they did in ISP. It was viewed as a more minor side event for fun, despite how intense some of the matches got later on. The top complaints or gripes were over Smashballs: not many people wanted them on, or saw them as not contributing towards something skillful. A few went further, and said the Smashball limit was basically proof that the item was too much if you were required to further limit how often players got/used it.
Things might have been different if Smashballs were not included at all, but I can honestly say the inclusion of them was a huge mistake and turned a LOT of people off to the idea of items. ISP was seen as arbitrary on what items got in vs what items did not, and Smashballs helped none in that regard. Maybe you were at the event, and heard differently from players around you. I got to personally talk with some of the best players in the country before/during/after the event, and I don't think their opinion was changed in a positive way towards items or ISP. I'm not sure who you are speaking for, or if you were personally there, but I was there and disagree with the premise that everyone liked ISP/items but didn't have the guts to advocate for it due to public pressure. It was basically an open secret that people didn't like items. Still is lol (unfair stigma or not, it's obvious)